Yep, I agree on the 1/2 inch. Apparently some folks are using it, as mentioned by the op. Maybe they cut it up in pieces and put it only in certain spots like the factory padding on carpet.
If it has the metal foil on it like most, THAT would be good to go on the underside of the car. .....even still it's too thick and heavy "for me". The dang killmat is heavy enough.
