Conley,
I've toyed with the idea too, actually I'm working on that right now. Welding sheet metal Stainless is not easy, and the heat treeatment poses a problem. first welding the floorplate to untreated tubes, and then heat treating it is a possibility, but then the heat treatment gets tricky, you have to have the right treatment for the specific alloy. I'm working on that, and possibly cutting down full size mags, and crimping the floorplate and then brazing or silver soldering it in place. When I have something that works, I'll post it on here.