Painting the trunks/engine bay/underside/cabin, POR-15 and leave black? Options

[boxsterfan]

I have been thinking about what I will do with my car in the future when it comes time to restore. On many cars, I see people have appeared to POR-15 (or other) the trunks/engine bay/underside/cabin and then left it black? They then go on to paint the rest of the car as normal (orange, red, white, green, etc...)

I'm not looking to build a concourse winner myself. I am looking to build a car that is restored and protected from rust for as long as possible (another 40 years lets say).

What do people think of POR-15'ing (or any other product) the trunks/engine bay/underside/cabin and then leaving those areas as that? And then (in my case blue) painting the rest of the car as normal?

[sixaddict]

The subject has been covered pretty well.....but one thing I had read about it...If you plan on top coating ( as you should) it must be done very soon after applying POR. I have heard many complain about it peeling and have seen it on a car.

I couple of years ago I consulted a NJ Porsche restoration expert about it.....He seemed reluctant to speak to my specific question but gave me two alternatives with very lengthy explanations. That told me he was not a believer.
He recommended two things
Benjamin Moore Ironclad primer ( Have it in the garage) and Rustoleum damp proof primer ( don't look for it at big box home enters) ...Both come from specialized paint stores.

I have used in interiors after stripping tar and cleaning up. Add new tar and then do Urethane color. A PITA but I like results. In engine bay it could work but have not used to date. AS you see like belly buttons everyone has an opinion.
Good luck