I am having the same problem, I do know one thing, after hours of changing this and that to get the elevator halves the same, The longer rod on one side makes no difference in the deflection. If you have your servo arms exactly straight up on each side, It does not matter of the arm is 4 inches or 6 inches. the geometry difference is changed only in the servo arm length and the control arm length. I ran out of options and replaced both servos thinking that the problem was with them,...WRONG! I need help too. Right now I have the control rods in different holes (which is stupid) but the halves function closest this way. My plane flies great, the only time that I can tell is when the plane is at full elevator and it rolls to one side which I correct with the alerons. Help us you guys!