Interesting Montana, did you use POR15 Rust Preventative Paint or the POR15 topcoat?
My experience has been with POR15 Rust Preventative Paint. The main issue I found with the POR15 Rust Preventative Paint is that UV light turns it a tad grey, I don’t think this matters other than appearence though, alternatively it can be over painted with POR15 Top Coat which I chose to do sometimes but I understand it is not a requirement if the UV light effect does not matter.
The Rust preventative Paint can be used on rusty surfaces or old paint etc. I just wire brused and sometimes sanded, the toughest results I had was on rusty surfaces just wire brushed.
Roy