just something to keep in mind on the por15, i have used it quite a few times in different situations when restoring old cars, it is not intended to be applied over existing paint or coatings, its specifically designed to be applied over rusted or properly prepped bare metal. por stands for paint over rust. when applied to paint ed surfaces its only as strong as the paint under it, & even on bare metal it can & will flake off sooner than expected or advertised.
there are much better ways to coat the frame or any metal, eastwood makes a rust coating similar to por15 that most people say works better but still isnt designed for painted surfaces. i would look into a epoxy primer & use a quality automotive paint. or for coating painted areas & even rusted or bare metal good ol rustoleum brush on paint or the industrial version works very good. i live in iowa which has just as much snow/salt as almost any other northern state & rustoleum has lasted as long or longer than some por applications ive done.
nothing wrong with using por, just be aware of the correct way to use it & dont expect permanent results. also its not UV resistant & will turn a ugly greyish chalky color after a couple years if not properly top coated with a paint. all in all, ive got away from por.