DIY door panel

The thin moving blankets from Harbor Freight are cheap as hell work good for padding under your vinyl or material as well as on the panel backs.
Mattress stores usually have a dumpster in the back with nice heavy plastic used to cover them in shipping.
I used the blanket material and plastic on the backs of the panels for sound and insulation as well as a moisture barrier.
The blanket material is thin enough so it doesn't interfere with the clips holding, and once installed you can't tell it's there.
Just leave the plastic unglued along the bottom of the panels for breathing.