I have been going through the same thing, w/ many different oppinions on repairing methods, I had to cut a small section out of mine, and was able cut a patch out of an extra rear cross member I had. The gage appears to be 10ga if I am correct, I measured mine on one of the rear legs w/ a gauge. I cut mine out fitted the replacement section and then beveled the edges of both the patch and the chassis. I welded it in place w/ my Mig welder. I was talking to a guy the other day and he mentioned heating this area up before one welded w/ a Mig to get better penetration, I do not know if this is true?