John its been done many times pretty easy really
several different ways to go about it if you want to hide the servo with just a horn sticking out for the pushrod install 2 mounting rails in the wing at the servo location for the plate to screw to,then make a plywood plate for the servo mount between the ribs,using some small blocks glued to the back of the ply plate will work for the servo mounting screws, its typical ARF style.
if you dont mind the servo exposed, and have enough space in the wing for the servo to be mounted upright, then some basswood or similar, mounting rails placed from rib to rib with the proper spacing for the servo is also fine, you will need to frame in the area with some balsa,just some 1/4x1/4 pieces so you can cover the wing to the servo mount its pretty simple.

here is a typical servo mounting on a ply plate from a model I have for reference