I have been out in the cave mulling it over most of the afternoon and it really looks like the only viable option at this point is to tack the seam along the edge and then weld teh holes for the plug welds shut and grid them smooth. There is no way (at least with any of the tools that I have) to get behind the extension flange to hammer anything around. It is only along the ~ 6" section along the bottom of the wheel well opening that would be like this so there should be no compromise in strength. Thanks. L8r