Okay,
Here are those pictures I promised. The servo is mounted to a pair of hardwood blocks in the usual way. That assembly slides into the wing cavity, hooks onto the long pushrod and is held captive by another pair of blocks that are epoxyed into the wing. That has to be a tight slip fit so the servo cannot move from side to side. The rod that runs the length of the wing and and hooks to the belcranks helps to keep the servo in place forward and aft. The servo is then held down by a plywood strap and two servo screws. Simple really.
Oh, the crack you see in the wing came from an incounter with the ground during a stall on a take off. Be very careful boys, this is a touchy aircraft.