Here are what my rookie eyes see:
Based on the reputation and general flight characteristics of a warbird (especially with the wing design of the Corsair) I would opt for a light weight four stroke. H9's site did reviews with a Saito 1.00: the fit looks really good with just the tappet covers clearing the cowl. It is substantially lighter than something like an OS 1.20 four stroke, and appears to have plenty of power for sport-scale flying. The plane is not designed to be an all-out aerobat, so I don't see a need for over-powering and weighting down the plane.

I have a Venus II with a 1.20 two stroke, and it weighs just under 9lbs. While this is a totally different style plane, it still has over 110 square inches more wing area than the corsair, and is approximately the same weight. I like the idea of scale planes and scale flying, but if I can shave weight and improve flight characteristics, I will. I flew a Decathlon with a few different setups, one which included some extra on-board weight - it was a lot less fun to fly that way.

I probably have the least amount of experience out of anyone else in this thread so take this with a grain of salt.