You guys might want to rethink POR 15. I've been using that stuff for years and although it's durable (not as durable as powder coating) it doesn't stick to anything very well. I've gone round and round with the tech people at POR 15, spent a forture on all their prep. products (Marine Clean, Metal Ready, etc.) and still have problems with it peeling. I'm on the 3rd repaint of the undercarriage of a truck I did with it. It goes about 2 or 3 years before it start peeling. Also, POR 15 is Ultra Violate sensative. It will need to be painted with POR 15 Top Coat if it is to be in the sun.
I switched to the Eastwood Product, Rust Encapsulator. I saw a test report in one of the car magazines a while back that rated this product over POR 15. It's only been on for several months, so I'm not sure if it really is better, but the application process is much easier and it'll stand up to sun with out a top coat. There aren't as many colors available ... yet.
Eric M.