I have a Fox 3.2 (52cc) on the GP Pitts.

It balances perfect with 2 JR4721 elevator servos in the tail. 1 JR 4721 rudder servo in the tail. And 1 JR911 tailwheel servo in the tail.

My tank is on the CG. My throttle servo is about 3" forward of the back of the wing saddle. My RX and both 2100mah 6V MH batteries are also on the same tray as the throttle servo. Thats all just slightly in front of the rear point of the bottom wing saddle.

I mounted my engine and all my servos, then I made a tray for the throttle servo, RX, and batteries. There is a spot inside the fuse where you can slide that tray back and forth about 7" between the middle and the back of the wing saddle.

I'm using DuBro Heavy Duty .40-.91 control horns on my ailerons. Stock # 867 I have 4 aileron servos. JR4721

I'm using DuBro #866 HD control horns on the elevators and the rudder.

Probably too much detail, but I wanted to give you an idea of where most of my weight was at.