RE: UPDATE Hate it when the expiration date matches the maiden..
An older gentleman at my club asked someone else to fly his little 20 size trainer for the second time. There was only that gentleman, another, and me at the field all that day. The maiden flight was performed by the other guy (Kenny) while I flew my P-51. I agreed to fly it since the other guy was busy. The takeoff was good, but I would set the trim, take it in a turn and find myself re-trimming the ailerons. This made me very nervous, so I asked the guy if there was any tricks or anything he wanted me to perform. He said bring it in for a landing and he'll take it from there.
I brought it in a left turn, and after a landing where I was holding the ailerons to the right slightly we found out the servo horn was too big for the servo.
He used a hitec servo arm on a futaba servo, or vice-versa. I can't remember which.
Moral of the story: Make sure the servo arm cannot ever turn without the servo turning and that it fits TIGHT on the servo.