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?

[jcd914]

While prepping a friends 914 race car we actually wet down the bare metal after stripping and allowed it to start surface rusting before we painted over with POR.
We had been told it would help with adhesion.
The POR we use was gray and we did not paint over it, that was a mistake. After several weeks the areas that were routinely exposed to sun started turning a greenish tint. (IMG:style_emoticons/default/icon8.gif)

The 914 I just bought had been stripped to bare metal and repainted. The engine bay is painted black, trunks are black bed liner and the car is dark blue, Majik Blue Pearl to be exact. I love the combination.

Jim