So you are saying that because of the many possible differences in body proportions between different players, the optimal configuration of a racket can vary considerably? That would make sense to me.
This leaves one crucial component in your theory I never understood. In your formula there is only one acceleration term, g, which in your posts you have related to a high take-back. Does this mean that the primary force acting on the racket in your model is gravity? In other words, that in your model the tennis stroke is treated as a dual pendulum consisting of racket and arm swung through an arc from the highest takeback position by the force of gravity alone?
Does your model account for the acceleration of the racket and arm due to the hip and shoulder turn? Why is there no term in your formula which expresses this acceleration?
2 x Dunlop 4D200 Tour, full bed BHBR16 @ 36-38 lbs, tailweighted to ~10 pts HL, 374g