JimG,
According to the POR-15 website frequently asked questions: WILL THE SUN DESTROY MY POR-15 COATING IF I DON'T TOPCOAT IT?
No, your POR-15 protection will remain, but the sun will change its appearance cosmetically. That's why we recommend you topcoat it.
I'm not sure what they mean by "change its appearance cosmetically", but I describe it as blistering if left in direct sunlight. Could have been a chemical reaction to something I used to prep the surface, but I didn't want to repeat the mistake, and have topcoated everything since then. I don't know when they changed to UV resistant topcoats. It was available a year ago when I bought it.
Regarding lifting the body a few inches, I'm warming up to that idea. My wife has a greedy issue about taking up the other half of our two car garage.
Randy

Thanks for the encouragement.

You folks are all very entertaining, even when you are just haggeling.

I have used black Por-15 to touch up the trailer hitch on my modern car.The black turned gray where the sun contacted it..other than that the rust has not spread and the coating is holding up well for a few years now.

Hey JunkYardDog, are you OK? I was afraid you was out there with your doghouse raised up a couple of feet, painting the underneath with POR15 and got your paws covered with that black stuff and got stuck to the doghouse! Hello!

Sure I'm okay! Absolutely doing fine! And, one reason why I am doing fine is because I don't use POR-15 with all of it's disadvantages like getting it on your skin (in my case fur), or breathing the toxic stuff and etc. Won't allow it anywhere near my doghouse!! Yep, everything is cool here! Bow Wow!

Well , JunkYardDog I am glad you are clean (relatively, haven't been chaseing any polecats?) and C@@L!