Larry, The palm nailer is just helpful when you need to hammer from inside close quarters and don't have enough room to swing a hammer. Some of the work on this tank had to be hammered from inside with the dolly on the outside. Most of it was done the other way, dolly inside and hammer from outside.
I'm making progress on the tank. I made two steel rings from 3/16" plate and drilled bolt holes in them before installing them on the inside of each of the holes. I used panel bond to hold them in place and seal them. Then I riveted them in to hold them until the panel bond cures. The other holes in the plates are for screws that will hold the pump and level sensor. The green O rings go on first, then the pump and sensor, then the retaining rings are bolted on.