This session continued the prep of the fuel tank nose ribs. Two of the ribs each needed an additional 3/4" hole made with a step drill, with mounting holes around its perimeter made for a bung hole fitting. The mount holes also had to be match drilled for the bung holes that already existed in each of those ribs.
Then I continued to debur the edges and rivet holes on the rest of the ribs, and then countersinking the flange holes of those nose ribs that would eventually be facing the exterior tank skins. One of the holes in each of two ribs had extremely tight space on the back side that prevented use of my squeezer for dimpling, so I had to figure out how to use the close quarters dimpling tool. I ended up screwing the fixture to the top of my workbench, holding a dimpling die in place with tape, and then using a hammer to repeatedly strike the dimple die through the rib and into the fixture.