Original metal gauge was more like 18-19 ga. The quarter we just got from Layson's is around .045, which is in the 18-19 ga range. If you can get good with 22 ga, then standard replacement panels will be a snap.
When you do a lap weld, you would like to focus more time with the heat on the underlying metal; the exposed edge will gain heat MUCH faster than the underlying piece. With a constant filler speed of the MIG process, it is harder to do this compared to oxy or TIG, where you can put heat into the underlying metal to get it to puddle without adding filler for a short time, then direct heat into the edge and add filler to complete the weld. But the total heat of the MIG process is lower...important for sheet. I am getting ready to work some MIG sheet metal welds, so I'll let you know any breakthroughs.
