so i picked up a old sportster tank a few weeks back and i have decided to flatten the bottom so there will be no tunnel, and move the petcock bac, and the filler up. i am wondering the best way to go about this? i am thinking to just start cutting it up so once it is apart i can give the metal a good cleaning and have better access to knock out all the dents(it has a lot of them and a few big ones, with a really bad bondo job to match). then how would i go about sealing it? any help would be appreciated.