This question was asked in post 111 and no one seemed to pick up on my comments. There's a fundamental problem with the servo/elevator set-up on this plane: the servo axis to elevator axis distance is different between the servos (vertically). Unless you can actually control each servo's travel (its complete range- not just centering and endpoint), the elevator halves are not going to be in-sync. The output curve (actual movement of the elevator halve) will not match on both sides. The simple and proper solution is to raise (or lower) one of the servos so its axis is in line with the other.