Started off priming the # 8 nutplates for the flange, and then taped off the flange and primed the flange where I countersinked for the rivets.
Clecoed the nutplates to the flange with one cleco and then set the AN426AD3-4 flush rivet. Once the rivets were squeezed, remmoved the cleco, and squeezed the second rivet. I ended up drilling out 3 rivets that were a little proud on the flange. No issues with those.
Finished all four flanges. I still have to rivet on the #6 nutplates for the inspection panels and then countersink for the #8 and #6 holes once that's done.