Anything about 3/16" or less, I was able to fill with my MIG. Just crank the wire speed up and go in spurts, letting the previous weld cool before zapping another one. There were two spots where I miss-measured that I had to patch with sheet metal. The one on the main hoop, I made a patch and butt welded it (first photo). The other spot (front outrigger), I made a patch and overlapped it by 1/2" or so. I just made sure to seam seal the under side to prevent water getting into the overlapped area on the bottom. I'm kinda anal retentive about that. Hope this helps.
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