Originally Posted by pvaudio
You have made a huge amount of inference based on something that has never proven to be true. In fact, your reasoning is exactly opposite. The fact that there is less deflection means that the incoming ball's energy goes elsewhere. Compared to natural gut which will absorb an enormous amount of energy and return it, the stiffness in this case should do exactly opposite what you're saying. Think about it in extremes: a stringbed of a piece of wood vs. a stringbed made of rubber bands. Which will be more torsionally stable when hit with a huge ball?
Actually, your example helps make it easier to make my point.
A wooden paddle is much more torsionally stable than a stringbed made from rubber bands.
Consider what happens when a heavy ball with lots of topspin and pace hits the center of a rubber band stringbed:
The stringbed will deflect several inches. And because the ball has high rpm, it will not only deflect the stringbed in the normal direction, but the downward moving leading surface of the ball will grip the stringbed with friction and pull the center of the stringbed downward. The downward force vector acting on the stringbed is not within the plane of the stringbed -- rather, it is shifted several inches out of plane by the big deflection. The torque at a given time is the cross product of the downward force vector and the deflection - that is, the deflection = the moment arm. The bigger the deflection, the more torque acting on the stringbed to twist the frame.
In contrast, a wooden paddle has negligible deflection, so the moment arm is negligible, and the torque is negligible. Thus the wooden paddle is not twisted at all by a heavy ball, and makes for very accurate (albeit low-powered) volleying.
And your point about the ball's energy going elsewhere: it goes into ball flattening of course. Ball flattening means reduced power. But ball flattening also contributes significantly to spin generation, because the ball's rotational moment of inertia causes the ball's surface to move faster than the stringbed as the ball decompresses and its radius (i.e., distance from the stringbed to the ball's center) increases with a phenomenon know as "overspinning." I'm not making this up - it's been well-documented in lab tests.