take it to some one that has a housing jig to see if the housing is straight. you might be able to do this with a laser level. if you fine out its not straight have it fixed by the guy with the jig.
I agree. Doing it with a jig is the only way to do it right. When you go welding on metal you'd be surprised how it'll twist and distort, even if you just weld a little at a time. That's why you need a solid jig to hold it straight.