I've read the Mar-K test results, and have even painted my bed with the black exterior paint as their results support and they recommend. However, I ONLY used exterior paint- no POR 15. I don't understand what is the benefit of having an undercoat of POR 15. It has low UV resistance and depends on the exterior coats to protect it. If I have to maintain the outer coat to protect the base coat, then why not just use exterior all the way down? It's just wood.
Bill
