During the process of inspecting each rivet for blue fuel dye stains, my heart sank when I found a rivet hole without a rivet.
In the photo above, I have an alignment punch stabbed through the proseal filled hole. After much thought, and consultation from VAF, I decided to countersink the hole to accept a countersunk closed end blind rivet. The pictures below show before and after countersinking. For good measure, I was able to contort a piece of AL to slather a blob of sealant on the shop head of the rivet. The good news is that even if it didn't seal completely, the location of the rivet makes it highly unlikely to leak.