So the MgR/I theory only applies during the backswing phase while the racket drops from high to low. Can you illustrate graphically what you mean when you say "the final angle of the racquetface at the end of this gravity-powered first portion of the swing is nearly entirely determined by the MgR/I value" and "if MgR/I is not tuned, then the second part of the swing will begin with the racquetface not quite at the right orientation"? How does the racket face orientation change during this phase?
I always understood that you were referring to the racketface orientation at the end of the stroke when it strikes the ball. As I understand it (see for a more authoritative description this article by Rod Cross: http://www.racquetsportsindustry.com...ing_and_m.html
), the orientation of the racket face prior to impact changes as follows: During the second phase of the swing, as you defined it, the racketface first lags behind the wrist as the arm moves forward through the force applied by the player. Then, as the arm slows down at the end of the stroke, the racketface quickly catches up and accelerates forward through an arc around the wrist (dual pendulum), ideally striking the ball at the exact moment when the racketface is perpendicular to the intended hitting direction. Hence, slight variations in the timing of these processes during the second phase of the stroke will lead spraying of the ball from left to right. That's why I always thought you were referring to this second phase of the stroke when you were discussing MgI/R.
How does the timing of the first, backswing phase of the stroke affect the orientation of the racket face at impact? And doesn't the timing of the second, player-powered, phase of the stroke have a much more direct effect on the orientation of the racketface at impact and hence the accuracy of the shot?