POR is very overpriced. A similar, reliable, moisture curing product is Chassis Saver from Magnet paints.
http://magnetpaints.com/underbody.asp
I bought a can of POR clear and it performed horribly, I will never buy their products again.
I am convinced the oil rig story is BS
It
cannot lock drain plugs etc in place.
And be aware that 'testimonials', which someone was seeking, even our own here in this thread, are not scientific and are considered to be a form of propaganda (look it up). Only a study on multiple vehicles over several years under varying environmental conditions by an independent agency can be considered scientific. Which is way too expensive for any company to pay for, thus the oil rig story.
Try it if you wish. If you like it, wonderful. Good luck, and hold onto your wallet.