Originally Posted by FitzRoy
When I plugged those specs into your SGPR formula, it came out to 1.19. Do you think I've copied the formula incorrectly, or will some racquets serve well despite having a low SGPR number?
As stated when I posted the formula, it was only accurate up to 370 SW. At higher swingweights, there is not such a strong correlation between balance point and SGPR. One reason is that many pros with high swingweights in SW2 setups use very low tensions, so that the spin component on the groundstrokes is much higher. So these setups would feel overpowered if it weren't for the natural spin that brings groundstrokes back down into the court.
Nonetheless, based on my own experiments, I do believe that Federer's (apparent) balance point is a point or 2 more HL than the optimum for a 13-oz racquet for serves, but perfect for groundstrokes.