Don, I always have thoughts ...on any subject. :-)

I don't use PPG, so I can't offer much there.

If the dark red paint doesn't cover well, a red sealer will get you closer to the final color, and lessen the chance of the primer color peeking through somewhere.

I know guys who do successfully use clear over single stage, and clear is a little easier to sand. Just shoot it right after your single stage, or you will be faced with having to sand the whole thing just to get adhesion.

....and don't forget to show pictures of it to your friends. :-)