Another option to useing 2 servos in your wing is install both servos side by side in the center of the wing by enlargeing the servo mounting hole thats allready there on a high wing trainer type. Since most trainer planes are designed to use one single servo from this location, nothing is lost in servo torque by adding a second servo adjacent to it & this solves your extension issue. It also allows for easier trimming of the planes roll axis thru the radio instead of thru the clevis and keeps the added weight closer to the center of the fuse. This is SOP for all my trainers & opens up options like adding flapperons or spoilerons etc etc. if you want. Just another option....Gene