Well, that was VERY FRUSTRATING getting the first few rivets on the middle rib - flush and ... required several tries. Even had to drill out the first go at it. The final solution was to take and old PC and lay it on top of the skin to keep it from pulling the first rivet out as I was working the second one.... but I got all the rivets in - and the rib flange is flush against the skin. The process was not fun, but the result looks a little like part of an airplane! Won't be the prettiest, but looks a lot better than some of the airplanes I've rented.
Left side riveted!