You are always better off if each wing panel is cut from seperate pieces of foam. It makes the entire process much easier. The aileron hinge support should be imbedded in the foam prior to the sheeting being applied. A 1/4 inch sheet of balsa about two inches wide and a little longer than the aileron will do it. If it's too late for that use a dremel tool in their router support to remove the foam and sheeting. Their 1/2 inch drum sander adjusted to the correct depth works great for this but it does make a mess. Glue on the wing tip, except where the aileron is, and sand it to its final shape. Cut out the aileron after the wing tip is on. The portion of the wing tip that is removed is glued back into place. Remove enough of the aileron to have the sheeting cover the exposed foam and leave a 1/16 inch gap all around.