Final step is to sand the control surfaces so they blend in with the wing surface, trailing edge of the wing and wing tip to get a perfect match. Mark down where the slots are so after its covered, it will be easy finding the slots to glue on the control surfaces. I make mine 1 inch in from each end of the surface and then spaced 4 inches between hinges. This puts 6 in each aileron and 4 in each elevator.

Don