Back in the early 1970's I watched a body man on Okinawa fusion-weld a patch about 3" square into the middle of a door panel on a 57 Chevy sedan with a torch, with virtually no distortion. He used a tiny, needle-sharp flame and worked very quickly. He was good, to say the least! Later on, I used a similar technique to patch the front fenders on my M-151 Jeep where I had removed the turn signal mounts, with almost as good results. I needed to do a little metal finishing and shrinking afterwards, but no Bondo.
Jerry
