The Stovebolt Site Forums The Shop Area Paint and Body Shop Rusty inner roof; any suggestions?

You first sand/wire brush/flap grind the whole area looking for solid metal. Also looking for other rusted areas/bubbles. Then decide how a donor piece will fit. Like you said, you always cut it bigger and gradually trim and check, trim and check. When you trim the patch use a non aggressive approach/tool. Like a die grinder. Not an angle grinder. I don't know if you mean there is an inner wall and an outer wall. Anyway, the pinch weld is no harder to "line up" than anything else. Just use a "splint" on it while welding. Pinch welds can be worked/bent some. Watch out for warpage!!!!! I can tell you have the right plan in mind. Grit your teeth and cut it out.