A loose and/or spinning housing can split a factory fuel tank pretty easily and create a substantial fire. Nothing to fool with. Takes a pretty decent welder to make enough heat to get that stuff put together correctly.

A welded brace WILL bow the housing regardless being in a jig. The trick is to pull and hold the housing in the opposite direction the correct amount when welding it. Once cool, it will relax back to where it should be, if it was done correctly.