There was a time when all sorts of creative, albeit unrefined, methods of rust repair (we use that word loosely) were to simply cover it up with fiberglass, a chunk of sheetmetal screwed into place, ...
It seems as though you never have the time to get to the projects that are most important. Seven years ago, we picked up this 1969 Mustang Coupe for my son Jason to build as a father and son project.