I'm semi talking out of my @ss when I ask this question because I have not yet done any panel replacement work, but I do have some experience with gas, mig and tig welding.

Why not butt weld the replacement section in? Some of the stuff I have read suggests that lap welding (with a flange) creates an area that is prone to rust again. A butt weld should also allow you to grind the welds down to create a seam that should be almost non-detectable. Again, I haven't done this on my car yet, but it sounds good in theory. I know I've seen it done this way in some of the mags.

Hopefully someone with some actual experience will chime in.

Anyone?? Anyone??