What to use for door panel backing

I'm almost done making the seats and now am starting to turn my thoughts to making door panels on a TR8 restomod.  Whats a good material for the door cards?  Stock was pressed cardboard.  Got lots of used door panels, but the cardboard doesn't hold up well at all.  Mounting holes get elongated and the bottoms waffle.  Want something new, moldable, and waterproof.  The tops need to bend over 180* and tuck into window channels.  Can't be more than 1/4" thick.  Wood is out of the question.  Anybody have any luck heating and molding some type of plastic sheet?  I seem to remember a discussion about something like that a few months ago.

OK, just remembered the name of the stuff.  Its called Kydex.  Any thoughts on how thick it needs to be?  Most of the stuff I see online is .060" thick.

The Google gave me this: http://www.supercub.org/forum/showthread.php?37559-Kydex-Forming-Interior-Panels

I used ABS sheet when I did my 69 Cougar door panels.  I wanted plastic for the same reasons you did.  It’s available in a variety of size sheets and thicknesses.  My panels used the stock steel curved section from the OEM pressboard panels.  Pics in my build thread if you’re interested.