I began to rivet the R-405PD... I noticed that the -7 rivet called for on the plans seemed a little short.
Instead of going with my first thought (Move up to a -8) I went a head and drove the -7 anyway. I checked the shop head and it was so close to minimum tolerances. In denile I drove a second -7, the rivet height was just not cutting it.
I finally went to the -8 and it seemed a bit to long... I drove it with acceptable tolerances. But I was afraid I would bend it over. I continued with the nut plate and used -8 and these turned out great.
I had to stop there... after sleeping on it... I inspected the -7 again, and will be drilling them out and replacing with a -8, but will remove about a 1/32" off to get the proper length. During a spin recovery the aerodynamic forced applied to this area is critical. In no way can I accept any rivet that is not perfect...
My humble opinion... (A&P) and who will be flying this thing anyway!!! hahaha... Me!