Bluescan, photofly, great questions. Take a look at the "Theory of Lift" thread in Tech Log - you might find some info there. Also, take a look at "
Pitching Moment".
For a good discussion on the aerodynamic center, find a book entitled, "Fundamentals of Flight" by Richard Shevell or take a look at this
book by Darroll Stinton.
PJ2