Would I have been better off not knowing?

If you're resto modding the car, why not cut out the whole tire well, and give your car a flat, usable trunk. you would have to make a fuel tank mount though. if you want to save the trunk well, and you try the copper backed weld method, and it still keeps blowing through,then the metal is too thin, an you will need to cut out a larger area patch. The main thing to remember, is never try to run a bead on sheet metal. It will warp every time. do tack welds on the patch. Moving to opposite sides to minimize heat. keep tacking the same way all around the patch until it is solid. Then grind away. And yes, on the east coast, that's an awesome body.