So the aileron top skin is installed first. It was initially a pain in the *ss but once you get going things go smoothly. Getting that bucking bar down to the spar was the hardest part. I am glad I have long fingers and skinny arms. I stuck some painters tape along the rear of the Aileron spar to prevent scuffing the spar. Once the spar rivet line was done, the rest was pretty easy. The bottom skin is instaled last followed by the trailing edge. NO OOPSIES!!!!!