Went to install the nutplates on the bottom skin access panel and lo and behold I could not get the dimpler in to dimple the holes because the z angle support angles around the hole were riveted in place. If you want the nutplates installed properly (with countersunk rivets) you must install them before installing the z angles. I had to drill them out, then dimple the holes and the nutplates and install with 3/16 flush rivets.
This is not the way Zenith shows installing them, they do so with a domed 3/16th rivet, which IMO is just wrong because the access cover will not then sit flat and this large hole in the fuselage bottom skin is a known entry point for CO2, so the access cover should sit flat for a good seal.
