Originally Posted by AJB
LeeD, the OP was specifically about the physics of pronation. From the content of your posts, it appears that - whatever your tennis skill level and on-court experience may be - you do not have any specialized knowledge of the physics of tennis.
I think the thread has traveled far from what the OP was getting at. I did notice that one poster did come to understand that you do actually hit down on the first serve, so I think someone has gotten something from the pics posted.