I thought about that, but it seamed too obvious.

I really would NOT use a Y harness on a couple 8411 aileron servos. You've got 2 servos on EACH wing and your using a Y harness. Thats no good. You really need to use a seperate extension on each servo and plug them into DIFFERENT ports on the RX. Mix it with the TX.

Or use a single Matchbox located inside the fuse. Run a SEPERATE extension from EACH servo into the Matchbox. Use the Matchbox to dial in the center points of all 4 servos and adjust the travel on each servo indivually.

It could be the gears. I'll concede that. But, either way, you don't have that plane set up right. Look at the gears and replace them if needed. Then follow my instructions and get a Matchbox or plug them into different ports in the RX and mix it with the TX.