Hi Abs, mine has a spot welded nut on the inside of the bung, but I also use a good spring washer, this stops the bolt from working loose, as for lining it up, I have filed a nice shiney spot around where the hole is (on the bung) and I seem to have no problem seeing this as I near the hole (in the exhaust), yours does sound like it's too tight a fit, it should be a good fit but not that tight. Have you checked the roundness of it? if its slightly oval it won't fit well, other then that, a real good sanding may work.
I have just reread that, and its all wrong in all sorts of ways.