I analyzed Federer inside out hard FH on the APAS System http://www.youtube.com/watch?v=pPLmCqGIotM
There are data about his arm speed and acceleration around the wrist during forward swing.
The picture demonstrates that Federer is able to increase acceleration/force of the arm from frame #1 to #9. The magnitude of the force declined after frame #9. Around impact, frame #24, acceleration decreased more than 70%.
So, he is not able to accelerate the arm significantly near impact. But, this is very hard FH and without doubt he is trying to produce maximum acceleration/force.
Question: What is wrong with Federer?
The answer will be tomorrow.