Thnx Bob.Bob Jewett said:Which is why one of the English players who used to participate in the on-line forums recommended a matchbox on its side. That allows the rocking which is normal for a still-elbow stroke (pendulum) but prevents swooping.
I think a piston stroke, which is what a bottle requires or at least encourages, is more complicated mechanically, and unless someone can come up with a real good physical argument in its favor, I think it should be avoided by beginners. Whether it helps anyone is a hard thing to determine. Jeremy Jones and Lori Jon Jones both have piston strokes, as do some top snooker players.
I thought Jeremy Jones had a stroke-slip.