I was talking with a guy in the staging lanes a couple of weeks ago that I noted had recently added a bar to his car, a Dart, that has a real nice interior. I specifically asked about the upper welds and the headliner. His answer was simple, yet brilliant. He cut holes in the floor where the plates were to be welded in, dropped the bar through the holes to give room to weld the upper section of the rear supports to the main hoop, then raised it back up and slid in the mounting plates and made those welds. He then replaced the holes in the floor under the plates, tacking them and filling with seamseal adhesive.

This may be an old trick, but I hadn't thought of it nor ever heard of anyone using it; and it allowed him to get the bar tight to the roof and fully welded without even removing the headliner.