The standard install for elev/rudd servos are above the wing, but I think you could mount them aft. It would just require more thought and work. Since this is not a 2m plane, I did not get fancy. I even used the wooden dowel for the elevator pushrod, which works quite well. The only deviation I made was mount the elevator servo on it's side so that there was no side-side movement of the pushrod.

Someone on this thread has described which version of the bolly gear. I believe it is the standard or smallest size.