[chris vickery]

Thought I would jump in here on this one.
The guy that does some sandblasting for me has an autobody shop. 99% of the repairs he makes now are by using some sort of panel adhesive.
He swears by it, the setup is quick, no heat and warpage and no risk of fires.
His procedure is straightforeward; he cuts out the damaged area, uses a pneumatic tool to make a flange all the way round, fits the patch and uses a few self tapping screws to secure. Once happy with the fit he simply removes the patch panel, applies the glue and re-attaches it in place. An hour later he removes the self tappers and its ready for a small skim of Bondo and viola, finished.
I have seen repairs done and it does a better job than welding in a quarter of the time.