Dear Jamie,
That's a very difficult topic to speak about accurately. I haven't really gotten my thinking straight about this yet, but let me share my present assessment. Basically, there are a number of factors that are at play in whether your putter toe will flare open in the backstroke, not just hand manipulation and stroke path. Let me start with some pertinent observations or guidelines for putting I've found important. Then we can discuss toe opening and what to do about it.
First, putterface squareness is more important than sweetspot contact. So if the path makes it apparent that you're not going to make contact with the sweetspot, you still need to keep the face square. This thought tends to reduce the importance of keeping the stroke straight, at least in the backstroke and most of the forward stroke.
Second, the only part of the stroke that really matters is the last part of the downstroke past the middle of the stance, which is where the stroke truly becomes a "forward" stroke to send the ball "away" from your setup. This is where the face needs to be square, if it has wandered out of square before this point. So this is where any arcing stroke path has to get square and stay square.
Third, it's not really best to think of a stroke path inside-square-inside as being "normal" because in fact (in my experience) you really want the face to stay square through impact. The putterface-ball contact is not really instantaneous, but lasts for a few inches depending upon your putterface material, ball, green speed, and stroke pace. A slow tempo metal-face putter on a balata ball on a mid-speed green will stay in contact with the ball for up to three inches. What many people describe as the classic inside-square-inside stroke of Ben Crenshaw is not really all that "inside" in the thru-stroke. Instead, it is more of a straight-away stroke that results in a rising up of the left side thru impact as the putterhead moves down the line. Sure the putterhead curls inside at some point past the ball, but right thru impact and sometimes quite a ways past impact (say, one foot) the best putters keep the blade headed square down the line. Dave Stockton explicitly teaches this feature in the stroke for the path and wrists to keep the face headed square past the ball, regardless of what went on with the path or wrists in the stroke behind the ball.
The movement in the wrist that you describe has been known in putting for about 100 years. In the 1920s it was called "hooding" the putter. Hooding is a "counterclockwise" rotation of the wrists as the stroke goes back away from the ball. You use the term "reverse" to describe the movement. For a right-hander, this means the thumbs rotate towards the target while taking the putter back. The action counteracts the inside-arcing stroke path by manipulating the putterface orientation to keep it flush to the way it started. So, although the hosel of the putter sweeps inside, the rotation of the wrists keeps the putterface aimed the same way it was at address. Actually, the putterface is not aimed at the same target, but is oriented the same way with respect to the feet and stance as it was at the start. Once the forward stroke begins, you have to "unwind" the hooding in the opposite way precisely as the rotation went back, so the putter stays with that orientation and the arcing of the path returns the face square at impact.
Horton Smith in the 1930s and 1940s taught this technique, but he also taught keeping the face squarely headed down the line thru impact. This frequently required an extension of the lead elbow to sort of "shoot" the face square down the line.
Bobby Locke in the 1940s and 1950s elaborated on this wrist action by combining it with a closed stance. His path came back along his toe line, with the right foot back about 4 inches from the puttline than the left foot. The hooding action is about the same this way, but the thru stroke is the big difference. Locke's path forward follows the toe line back to the middle of his stance, but then his right shoulder comes laterally out and he delivers the putterface squarely down the line thru impact and beyond, with a slight rising of the putterhead thru impact to hit up thru the ball. So his path is sort of straight back along the toes, and then the shoulders pivot the stroke path onto a straight path down the line. Locke appears not to have "unwound" his wrists coming into the ball, but instead "froze" the hooding action of the wrists when they reached the top of the backstroke. So, effectively, his return of the face was handled by the right shoulder move. The putter actually came at the ball from the inside but the face was aimed square at impact, and he timed the shoulder move so that once the face arrived at the ball the path was not cutting inside-to-out but was then headed straight down the line. His impact was that of a square face moving square down the line with an upward rising blow to start the roll straight.
Loren Roberts and Gil Morgan both have a faint echo of this old technique. Both allow some folding or breaking of the wrists going to the top of the backstroke, and then fix the wrists for the remainder of the stroke. The folding of the wrists can be managed with the hanging of the arms below the shoulder sockets so that the fold is oriented like a pet door, so that the putterface lifts and delofts, but is not turned aside so the toe flares open. Toe and heel stay coordinated and flush even though the wrists break going to the top. This pretty much requires the hands to be not only below the shoulder sockets, but also below the elbow joints too. In this connection, so-called "high hands" with the backs of the tumbs made striaght with the inside edges of the forearms, like a fly fisherman's cast action, helps promote this keeping of the wrist break in avertical plane so the delofting is even and not askew. Almost all good putters have this downward bend in the wrists at address.
With respect to your experience with a stroke track, I would suggest that your setup and hand position influence the need for some hooding action to keep the putterface square. If you're a bit back away from the ball, you will have a greater arcing of the path and a corresponding greater "hooding" action required to stay straight inside a track. That setup has the elbows below the shoulder sockets but the hands out towards the ball more. As the backstroke progresses and gets past about 1-2 feet, this hands position starts to tell by requiring the path to arc inside.
But even back a bit, you can still stay straight with a "no-hands" shoulder stroke so long as your biomechanics are correct, up to a point. The trouble usually is that this sort of biomechanics with feet a bit back from the ball makes you feel like you're leaning under during the backstroke. Most people who go for this think their heads are swaying going back as their face leans a bit. The putter also seems to rise. This all results from hands and/or elbows in the vertical plane below the shoulder sockets, STAYING in this plane. In order for the hands to remain the same distance from the track at all points in the stroke, and therefore keep the putterhead moving inside a straight track, you really really have to send the right shoulder high and keep it in that vertical plane and also keep the left shoulder coming down in that plane.
In other words, send your left shoulder straight down towards your left hip, folding your torso at the left waist. Ultimately, that's where the true pendulum shoulder stroke is headed. What really happens is that once the bottom of the rib cage on the left goes down and starts to meet resistance from the pelvis and abdominal muscles, the torso wanders out of the vertical plane and the left shoulder comes forward so the rib cage can clear the pelvis area and keep headed down without resistance. As the torso turns latertally to keep coming down, the right shoulder moves laterally back and the right hip wants to move back, too. So a pendulum stroke with shoulder remaining in the vertical plane rocking back does not run into this problem area until the stroke length going back reaches beyond about two feet.
If you try not to let the shoulders wander laterally out of the vertical plane, you will feel like your head is inside a big laundry drying machine. The head roll that often accompanies a big pendulum backstroke just usually convinces people to forget it and let the stroke arc inside. But really it is quite possible to have your pendulum stroke in this range and keep the head level and still, too. It just requires separatingthe base of the neck from the shoulder rock, keeping the base of the neck still while the shoulders rock beneath it.
Now, to catalog factors influencing toe opening in the backstroke:
1) putter design with heel shafting promotes toe flaring open (but does not promote the toe closing coming forward or past impact -- that's a myth);
2) putter design with heel-toe weighting to "widen" the sweetspot, combined with heel shafting, practically guarantees the toe will flare open going back and makes the transition of putterhead direction at the top of the backstroke more problematic because the toe has extra momentum and wants to keep headed back and opening;
3) standing more upright at address (like Crenshaw) makes the ribcage conflict sooner with the pelvis, in contrast to a setup that has the torso bent out or canted forward more, with the result that the arcing starts sooner and is more pronounced, and can often feature a bit of right knee action in the putt (also like Crenshaw) indicating the right hip clearing out of the way going back;
4) having the hands out towards the ball combined with not keeping the shoulder turn in the vertical plane, which causes problem after about 1 or 2 feet of backstroke;
5) simply not keeping the shoulder turn in the vertical plane, which causes problem after about 1 or 2 feet of backstroke regardless of whether the hands are beneath the shoulders;
6) deliberately manipulating the wrists to alter the putterface orientation in the stroke (hooding, or allowing wrists break that is not vertically oriented for true even delofting).
So long as the length of the backstroke stays within about 2 feet, the problem is not very noticeable, or at least is manageable. Trying to keep the shoulder turn more vertical in the problem area while keeping the neck still is also helpful. And a center-shafted putter without heel-toe weighting also helps minimize toe flaring.
What happens with the face going forward is another story altogether. If your stroke is "gating" around the body in an arc inside-square-inside, because you stand tall like Crenshaw, AND you truly have no hand manipulations, the face can/will stay aimed into the curve of the path. Wherever the path is aimed, the face is square to the path at that point in the stroke. So theoretically, when your stroke returns to impact, the putter will be square to the original orientation you decided was right when you first set the face behind the ball. Of course, it's not that simple because of problems in how you turn the torso back and thru in the stroke.
But in any event, heel-shafted putters and heel-toe weighted putter still exacerbate the toe action. The toe actually flares MORE than the arcing of the stroke, so in this case the face is not even sqaure into the path, but gets open.
What would close the toe back coming forward? The stroke path itself won't do it, if you really have a no-hands stroke. There would have to be something artificial about the movement forward to insure that the toe gets closed back to square for impact. Without hand manipulation, the only other way to do it is with the right shoulder coming laterally forward in the downstroke -- more than it would in just the natural arcing of the stroke. This is very odd feeling, so almost everyone in this situation uses the hands to get the putter's toe closed back to square, and eventually, they tighten grip pressure to try to minimize the flaring going back to start with. Ultimately, heel-toe weighting and heel-shafted putters have to go -- no good for good putters.
If you look at Nicklaus' setup and stroke action, you'll see he aims the face square, tries to keep it square coming back, and then "pushes" the face square down the line. This causes his left elbow to move straight parallel to the putt path and this separates the elbow from the left hip past impact. That's not normal. In normal human motion, the elbows want to stay close to the hips as the torso twists left or right. But in putting, in the thru-stroke, if the elbows stay with the hips past impact, you get a pull as the left elbow drags the face closed and left along with it's following the hip.
Again, in the shoulder pendulum stroke, if the left shoulder goes down at the hip in a vertical plane, and then rises vertically from that hip, there is little or no impetus in the body to send the hips turning in the stroke. And in that action, as the left shoulder rises coming thru impact, the elbow separates from the hip. This doesn't happen by flapping the arms farther from the torso, by the way. In the shoulder stroke, the arm pits stay pretty much closed and unchanging in the stroke. If you cant the torso forward in the setup, so that the shoulder sockets end up above the balls of the feet or the big toes, the elbows ought to stay moving straight along the toe line parallel to the puttline thru impact. This will send the left elbow straight away from the left hip.
With this sort of action, you can get a pendulum stroke that pretty much keeps the face square going back and then forward. If you have some toe flaring open going back, you'll have to do something about it other than just have a natural stroke path in order to get the toe closed and square thru impact. Just an inside-square-inside path won't be enough if the toe gets open to the arc.
If you have some toe flaring going back, and don't want to alter your putter or your setup, or your stroke movement, then try adding a little extra pressure in your left thumb onto the top of the handle. If both thumbs are normally a 3 on a scale of 1 to 10, try keeping the right thumb 3 and make the left thumb 4. This will tend to dampen out some of the flaring and shift your focus to moving the thumbs straight so that the bottoms of the thumbs and top of the handle keep the same plane in the stroke. You can think of reaching down to a thick sheet of safety glass with your grip and placing the thumbs on the outer surface and your index fingers on the underside of the glass edge, sort of pinching the glass edge. Then slide the thumbs back and thru along this smooth surface in a very straight line in plane.
When you get right down to it, all of this shows up the flaw in the very notion of a stroke track -- from Pelz or from anyone. They are not coordinated with your putter, your setup, or your stroke movement pattern. Trying to figure out a combination that fits the track is a little like Cinderella's stepmothers jamming their feet into the glass slipper. Unless you undertsand the body and the putter dynamics very deeply, you'll have a hard time using a stroke track trying to get some features out of the action that probably don't really matter much.
What you really want is some good action coming forward that delivers a square face headed down the line thru impact and a bit beyond. The details of making this happen have to account for your putter, your body, your setup, and your movement skills. The argument for the stroke track is that it will FORCE you to find THE BEST way to make this happen, but I don't and have never believed this. The backstroke is decidely different from the thrustroke, and even if there is a little toe opening going back, this is very likely required by your putter or your body or your setup. Your setup summarizes many subtle choices about positioning your body for the stroke action involved, and that depends upon the putter and your body and your movement skills. The setup is vital to your targeting and execution accuracy and consistency. So you DO want a setup that promotes a square face moving squarely down the line thru impact, but apart from this, the notion that the stroke track is THE ONLY acceptable or THE BEST path is simply false.
So my bottom-line advice is to take the stroke track with a big grain of salt. You might be better served setting a couple of 4x4 timbers to make a channel that only starts at the ball and then defines a lane down the line that is about 5 inches wide, and make your thru-stroke stay in this channel until the putter rises high enough to curve back inside.
I apologize for this being so longwinded, but conventional putting instruction over the last 25 years has created a lot of false notions that don't bear close critical scrutiny. It takes a while to untangle the mess.
Cheers!
Geoff Mangum
The PuttingZone.com
http://puttingzone.com