Body panel replacement tips/advice needed

Flanging invites rust. Mark where you want to cut out bad original, add 2". Then cut replacement to that size. Position it, and tech5 self- drilling screw at edges. Avoid any contours, match the contours. Now cut at 1 1/2" from edge, cutting new and old. A die grinder to start the hole, then a jigsaw with a 1/8" wide blade (you need 1/8" for weld contraction). Then cut both panels for 6", then peel back new panel from front, original from back, and tack(butt weld in several spots, with the wet rag right behind it.
Continue process, checking for warpage pushing outwards(means welds too hot, too close together, not cooled.). If it warps out, heat it(propane fine) and smack it in, letting the dolly behind it bounce off, when hit. Then slowly zap it closed. Make sure you take measurements, using a level from the floor, to all contours, and the bottom lip first, as you probably need to cut out the trunk extension, and replace it too.