Maybe this is what you already said. Not sure what a Zip cut is:
Another method on the curves would be to cut the donor piece "longer"/past the rust, place it on the truck and cut both at the same time. Then use "spacers" using the same thinckness cutting disc you used, while tacking....or registration cuts/marks. Check it all with the template and etc.
Many other countries do not have the same "auto insurance" we do. They NEVER total a car. They keep ALL crashed cars. The many, one or two guy, independent repair shops, get a donor for a whole section, including quarter panel with door opening, hatch opening, etc. They cut some of the damaged skin off/drill the spot welds, then "pull" the structure back to spec, weld and repair that hidden part, then they remove spot welds from the remainder bad skin. Then get the skin/sheet metal they need from the donor. Lay the whole piece on the car and cut them both at the same time, as I mentioned. Two difference there. Cars now are built with inner structure and outer skin, sort to speak, and secondly they have factory registration holes, or features, which the repair person uses to match up, as he cuts both at the same time. You get the picture to think about for your repair.
