D8 sounds VERY hefty for a putter! 60 grams added to the Odyssey head doesn't especially concern me, as the weights that start to be TOO MUCH for most people kick in somewhere around 450+ grams in the head. Your putter head is probably not much above 400 even with the added 60 grams.
For example, 641 mm from balance point to top with 575 grams total weight (head, shaft, grip) is a swingweight of D8. 641 mm is a 33.25" putter with a balance point 8 inches from the sole (just a wild guess for illustrative purposes). (Swingweight calculator.)
But when viewed as an issue of overall weight, the total weight is 575 grams. That's about 400-410 grams in the head and the rest in the shaft and grip (165-175). If the shaft alone is 120 grams, then the grip is 45-55 grams (a little lighter than usual). Nothing odd about that.
Winn putter grips are about 60 grams, and a few are closer to 80 grams. Karakal putter grips vary in the range 70-75 grams. Lamkin putter grips range mostly in the 60-70 grams area as well, with some in the 70-80 grams area and jumbos up to 112 grams.
In general full-swing club fitting, this observation is pertinent:
"The weight of a grip would be one of the most important specifications when you re-grip your golf clubs. Popular and widely used grips weigh at around 50 grams, while the weight of grips ranges from less than 20 grams to almost 70 grams. Majority of grips in the market, except for putter grips, are in the range of 40 – 55 grams.
Changing from a 50-gram grip to a 40-gram grip would increase the swing-weight up to 2 – 3 point depending on the shaft length, club weight and balance point. It should be noted that changing the weight of grip without considering the effect to the swing-weight could lead you to a undesirable result."
The same calculations work for the supposed 641 mm balance point to top of a 33.25" putter. Reducing the t5otal weight from 575 grams to 565 grams reduces the swingweight 3 points from D8 to D5. So if you want to adjust the swingweight without messing too much with your putter, just reduce the lead from 60 grams to 50 grams to move the swingweight from D8 to D5 etc. (10 grams out for every 3 points down in swingweight).
Incidentally, humans' ability to know the difference between weights in the hand is not that great. The so-called "Just Noticeable Difference" (JND) as measured in psychometrics is around 10%. That means a person cannot usually tell which of two suitcases is heavier when the difference is under 10%, as in one suitcase weighs 100 pounds and the other suitcase weighs 107 pounds. In putters, starting with a 575 gram total weight, you would have to change the weight by at least 58 grams before practically any golfer could tell the changed putter was heavier or lighter.
Cheers!
Geoff Mangum
Putting Coach and Theorist
PuttingZone.com
Golf's most advanced and comprehensive putting instruction.