The piston type stroke, with the right hand palm grip is the most reliable and generates the most FEEL for distance with putts. It also, as mentioned by others, has the fewest moving parts. Jack Nicklaus used this stroke, and let's face it, if you had a 6 footer for the freedom of the western world, there is no one in the history of golf you would rather have hit that putt.....
I cannot stress enough that the fewer moving parts in your putting stroke, the better it is, and it is NOT a pendulum. We can go further into the mechanics of that if anyone wishes. I am trying to put together a puttting video this weekend and post it for later perusal. Having trouble with my video camera.\
The major portions to putting are really very simple. 1 - be COMFORTABLE over the ball. 2 Stand so that you are STABLE over the ball. 3 hold the putter so that it feels comfortable in your hands and completely eliminates any wrist action whatsoever. 4 Hold the putter so that the palm of your dominant hand is on the grip (for distance fee). 5 KEEP YOUR HEAD STILL 6 ACCELERATE the putter through the ball, regardless of the distance or speed of the greens.
And MOST important. If you are an EXPERT putter, you will make slightly more that 50% of your 6 ' putts, and slightly more than 20% of your 10 foot putts, so don't beat your self up if you don't make'em all.
If you want to make more birdies, hit your approach shots closer to the hole
Obi WunPutt
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Understand accumulators. By having the grip under the heel pad of the left hand you are maximizing power. By having the grip under the thumb pad of the left hand you are minimizing power. Changing your left hand grip in this respect will change the travel distance of the club head. THerefore, your distance control can vary greatly with know more or less effort. So know,know,know your left hand grip.
THen understand which accumulators are in place and being utilized. Are you using #1 or #4? No wristcock is needed, so where does the putter lie in your left hand.
Now go to hinges. An angled hinge will feel like "no roll", the horizontal hinge will feel like "roll", and the vertical hinge will feel like a "reverse roll", unless your hinges have problems. There are visual equivalents you should look, look, look.
From here make your decision on how big or small your grips (on putter) should be.