Apologies for butting into this thread but I notice some people using the test hitting the ball down table and back to the tip as part of their testing. This test can be easily "cheated" with compensation for errors. This compensation could explain unexpected vibrations. The solution is simple, add a gate down table near where the cue ball is hitting the rail or add a second ball down there one diamond from the rail, or both. This insures that a person is hitting the rail where intended and not cheating the shot. A gate can be as simple as two balls, any two objects preferred, or an actual gate can be cut out of wood, cardboard, or whatever. Hopefully this will explain any mystery buzzes when the cue ball returns to the tip seeming to indicate a straight stroke and shot.
I am interested in this device as an aid to some exercises I do at home without a pool table so I am watching this thread with interest. I posted this to hopefully add to the accuracy of the testing.
Hu