Check tank integrity. I pulled a vacuum on the tank, about 2". It held several hours. Then I pressurized the tank, probably 2 or 3 PSI and it held pressure. So I felt that I had no major leaks. I got about 4 gal. of 100LL and filled the tank. After rollong the tank into several positions to make sure that every surface was submerged I used my A/C sniffer to check all the seams for leaks. It normally would sniff for R12 or HF-134 freon but it basiclly is just looking for hydrocarbons. If 100LL is not a hydrocarbon I don't know what is. Anyway I could not get even a wiff at any seams or rivets. All good!! Moiunted the tank to the front spar. Finally progress! Colecoed the upper skins to the ribs.