Reasonable, were the Model A Lebaron Bonney panels. I used to cut up micro-bus flat panels, and bond the upholstery to patterns cut from them.
The plastic cardboard like they make signs on the side of the road with. After and election u can find them everywhere.
I'm with 35window,I've seen guys use 1/8 pvc,works well and you can bend it with a little heat,I'm working n my interior now and plan on using pvc.
Expanded PVC gets my vote too. If you have a high end lumber yard around they might have it and it's lots cheaper. I think I was paying $80 for 3/4" 4x8 sheets.
Your local upholstery supply house will have waterproof (actually water resistant) panel board in a couple of different sizes. It's reasonable priced and easy to work with. You can cut it with a razor blade and it will hold a staple(s) for attaching your material. PVC might start showing some waves after being exposed to hot and cold, especially the larger panels. Another option is fiberboard, like you get at Lowes/Home Depot, but it's not as resistant to moisture. Just my $.02... Posted from the TJJ App for iPhone & iPad
PVC will actually "melt" and bend with enuff heat in the interior...or as a package tray. There is no such thing as "waterproof" cardboard...'water resistant' yes, but eventually it will warp if it ****s up too much water (rainwater or washing your car). Luan wood is the same as cardboard...it too, will **** up water and warp. Black 1/8" thick upholstery plastic is available from most upholstery supply houses in 4' x 8' sheets ...it won't warp from heat and will not **** up water but it is not cheap...of course, IF you want to re-do your door panels every couple of years cuz they've warped, use something cheap... R-
i use 1/8" white tile board you buy at lowes [it is used to go around a tub or shower] comes in 4x8 sheets
A friend of mine used bathroom paneling he bought on close out at a local big box home improvement store. It had chips and cracks but it was cheap.