I wanted to seal the outboard end rib to the tank skin tonight, but by the time I got the parts cleaned and prepped it was a bit late to start.
I removed both end ribs and the vent line, then re-cleaned all the prevously scuffed mating surfaces associated with the outboard end rib with solvent, including the T-410 reinforcment plate, and the rib's aft tooling hole. I also cut and cleaned an AN470-6-7 to a -5 length to fill the tooling hole. I then masked the inside of the outboard end of the skin, allowing at least 23/32" of clear area for the 11/16" of joint plate.
The next work session, I should be ready to seal and rivet.
Outboard end of the right tank skin masked to keep the mating surface to the joint plate sealant-free.