Dear Gregg,
By placing your weight more on the front foot, you are shifting the pivot targetward and also shifting the bottom of your stroke arc slightly targetward as well. And probably you are also tilting your shoulder frame lead-shoulder-down off level a bit. This combination ordinarily encourages a descending-blow impact thru the ball, but your ball placement is described as "well forward."
With this combination of setup and ball position, it is likely that you are simply bottoming out behind the ball and impactng the ball on a very slight upstroke. That's not bad. You could have a little more distance between the bottom of the stroke and the back of the ball without the weight-forward setup, but your setup is ok so long as you still have enough room to bottom out the stroke and get the stroke headed up and down the line before impact.
The effect you may be getting that is different is the isolation of the lead shoulder socket more directly above the bottom of the stroke. This shifts the sense of when the bottom is reached from when the torso is squarely aimed at the bottom of the stroke in the middle of the feet with both arms angling down at this bottom to a sense of when the lead arm has straightened out (more or less) directly above the bottom of the stroke (more or less -- not quite). Both senses of the bottom work well.
The difference is in the timing of the upstroke beginning at the bottom. The timing required is not as tight when there is more room from bottom of stroke to back of ball, compared to the relatively short window of opportunity to get the move right when the bottom of the stroke is right behind the ball.
The tilting of the shoulder frame could be a source of error too if the tilt gets the shoulder frame out of a vertical plane parallel to the putt plane (plane rising vertically out of the putt's start line). This is similar to the problem of the forward press -- if you aren't careful to forward press so the putter face closes evenly without any twist out of plane, you mess up. Similarly, setting up and then placing the weight forward accompanied with a slight dipping of the lead shoulder, the golfer has to be a little careful not to get the shoulders out of square.
Cheers!
Geoff Mangum
Putting Theorist and Instructor
Geoff Mangum's PuttingZone
http://puttingzone.com
Golf's most advanced and comprehensive putting instruction.
Over 600,000 visits and growing strong ...
518 Woodlawn Ave
Greensboro NC 27401
336.230.0612 home
336.402.1602 cell