AeroModding Material
 

So, after my roadtrip to/from Indianapolis last weekend, I've decided to make the front belly pan on my girlfriends Focus permanant, but due to the sagging I've already seen from the coroplast due to the heat I'm thinking of using a different material. The material I've been looking at is 1/8" think masonite (essentially a compressed particle hardwood) since it is relatively light-weight and quite solid and rigid. It can be cracked by a hard strike from a solid object, but I figure suck a strike would obliterate coroplast. Anybody have any other suggestions/ideas?

Why not just add stiffeners to the coroplast? Insert dowel rods of correct thickness where needed. Probably lighter and quieter than masonite, and you already did the work.

Heat: Use aluminum window screen material, held taught, near exhaust pipe, etc.. The aluminum screen is a superb heat conductor/dissipater, also breathes to let heat out while maintaining a relatively smooth aerodynamic surface.

I believe that you'll have problems using masonite; because it's subject to moisture damage. Masonite swells and falls apart when exposed to water.

I've worked with it in the past and it can easily be sealed to prevent moisture damage.

stiffners won't help when a jagged rock hits the coroplast, that and there aren't many places to attach braces to on the underside. The work I've done is only taped in place right now and would have to be removed to make it permanant anyway, plus I would use the original coroplast pieces as patterns to cut the masonite.

won't do any good since I want to keep the engine bay warm, the heat mainly comes from the radiator and the air coming out of it, the air flow coming from the radiator flows between the coroplast and the catalytic converter, so I doubt a heat shield there will do much good, I believe there is already an aluminum heat shield on the cat too.

Coroplast that gets hot enough to burn would melt and fall to the ground. Masonite, not so much. I'd feel better if you glued some foil or flashing onto the masonite where it's near really hot stuff. And, like you said, seal it up to keep the water from getting to it.

Yeah, I will likely lay a sheet of .020" Aluminum Flashing on the area nearest to the Cat