[dwtaylorpdx]

Coreplast also comes in an Aluminum version FYI.. There are several vendors of similar honeycomb AL materials. USed for LAB walls and cleanroom manufacturing. Comes in 4x8 and 4x16 sheets, cuts with a heavy utility knife (Score it) Or use a fine tooth carbide blade in a skillsaw, or a bandsaw.

FRP (Fiberglass reinforced plastic) is another option but its not as durable to heat, you need a few inches of separation.

Do not use wood under your car,, wood=fuel=fire,, add a oil leak and its going to go up fast.. (I work racetrack rescue I've seen a car fire a time or 20.... ) BTW no race car would get past me at tech with any wood on the chassis unless covered with a fire retarding coating.