Spotbiltxo:
I traced the cardboard panel off onto some thin paper today. I think its actually wrapping paper? Anyway, Its folded up in an envelop and on its way. I mailed it today before the post office closed so you should get it Monday or Tuesday. Just unfold it and lay something on it to flatten it back out.
I did notice the panels have "some" curvature on a couple edges but they are both the same. Just cut one and "flip it" to make the other side.
Glad to help out and keep us posted on what you do. I'm still debating what to do myself.
Before I retired I was working at a plant that makde the headliners for car manufactures. I have several pieces of it which is a 100% polyester that has been sheared and napped and then laminated to a thin foam backing. I think I may glue it to the carboard panels and....as someone suggested on the cardboard, put a coat of spar urethane on the back of it to keep it form asorbing moisture and warping.