Spar cap nut plates
I had a lot of difficulty getting the flush rivets that hold the nut plates onto the spar cap and ribs attached correctly. It took me a fair bit of trial and error before I figured out a way to position the pneumatic rivet squeezer so that it wouldn't interfere with the flange and so I could center it properly on the rivet despite only being able to see one side at a time. I did eventually get it to a place I liked, though I got a lot of practice drilling out rivets before I did.
Vertical stabilizer spar preparation
This post is from N212DM - Ben's RV-12is Build