The two humbs grip is similar to the Pure Pendulum grip made in Canada by Janis Zichmanis. The basic idea is to neutralize and level the shoulders at address (neither hand need be lower on the grip than the other as a forced consequence of the thinness of the grip -- plenty of room for both thumbs side by side) so that the return to impact is also level. Level is one of those symmetircally regular positions that the body knows very keenly from its regular dealings with gravity, as evolved over eons of experience.
Cheers!
Geoff Mangum
Putting Theorist and Instructor
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