You are preparing to embark on a voyage that has no end! Kind of exciting!! Yep, drop the tank. Gives you a better perspective back there, and makes it easier to work. The rear crossmember does not have to be welded on. It can be bolted, but many of us, including myself, have welded theirs. Have you thought about expenses and time involved?
Go Fish! <*////><
But the right word at the right time... "Hey, give me a little hug!" That's the difference between lightning and a harmless lightning bug!