I agree with Andy. Metal gear servos are a must. I think that it is unlikely that the string on the elevator caused the stripped nylon gear, but any hard landing or even a minor mid air can strip them. I use HS-82MG for elevator and throttle, and HS-85MG for the ailerons. Be sure to use a safety "slip joint" on your throttle linkage to avoid stripping the gears there. The Battle Axe plans show how it's done. Have FUN!