I replaced a tailpan and side panels on my '39 Ford two door sedan. When I welded the tailpan to the side panels I drilled holes in the tailpan flange and plug welded it to the side panels, which also had flanges. I welded another piece of sheet metal next to the flanges on the side panels since they were a little thin, making a double thickness. I didn't use enough heat the first time and need to re-do them. I drilled holes from the inside again but in order not to go through the outside flange, the holes are about 1/4-5/16 or so. Is this enough to get a good plug weld? This flange is about eight inches in length and I drilled five holes throughout. I'm pretty concerned about getting this right. Sorry for the long post, and thanks in advance, Rod.