I'm using 27-2900mah with the F3A with the Flight Power 3700's flying the new Masters sequence on a 22x12. Just switched to a 21x13 because of the wind and remembered why I used to like it..
This is in a 11lb 3 ounce Evolution..

Edit, I forgot to mention that I am flying in 20 mph wind + at these numbers. Still not used to the plane as it's only got 20 flights.
Numbers should come down I think to 25- 2800 mah I feel.

Chris