Have you ever tried bonding body panels on? I've used a 2-part epoxy that runs through a mixing nozzle on quarter panels, rocker panels and door skins. You do have to make a few short welds in high stress area, usually top and bottom corners, and clamp in place while it sets up. What I like about is that it's virtually warp free and you don't give corrosion a place to start. I know what a pain it is doing those individual spot welds the lenght of the quarter panel.
My dad uses this stuff a lot and is becoming quite a fan of it. He's trying to talk me into using it on a few spots on the 78 F-150 I'm doing.
