Well, I'm going to try it with hardboard. Same material I'll be using to make new door cards, also embossed with the diamond star. I might use a 1" layer of high density foam to keep the board from bouncing around. I'm going to put something called Deck Flash Barrier on first, kindof a poor man's dynamat.

I was also considering using that plastic painters drop cloth (heaviest mil I can find) as a moisture barrier for the doors. Think that will work or is there a better option?