I started riveting on the first three stiffeners on the left fuel tank tonight. I decided to re-dimple most of the skin because the rivets didn't seem to be sitting flush enough, so I adjusted the DRDT2 a little deeper. After dimpling, I loaded up all of the holes on the underside with rivets and taped them in place with blue painters' tape.

I mixed up a small plate of the tank sealant and applied it to each of the stiffeners using a popsicle stick, placed the stiffener over the protruding rivets, and then back-riveted them in place. I ended up having to drill a few rivets out because I noticed that they had topped over when my backrivet set slid a little bit due to the slipperyness of the wet tank sealant. Things seems to be more reliable if I use my other hand to hold the nose of the backrivet set against the skin so it can't slide while riveting.

I then covered each of the rivet shop-heads with a small blob of tank sealant by using a plastic drinking straw. I also attempted to apply extra tank sealant around the edge and smooth it into a fillet, but that ended up being pretty messy. I think I will try to apply a little more sealant on each stiffener in the future, so it oozes out under the edges and I don't need to apply extra afterwards.