After final closing the ailerons, I made a retaining bracket for the flap hinge pin. An inch of left over flap hinge was used. I cut the hinge so thatI had two eyelets and then matched drilled for 3-5 flush rivets.
Drilled a hole for the bolt and tested the fit.
Works great. I have a little bit of the hinge pin that has to be removed at each end.