I am trying to find the same hardboard to use for my 29 CCPU -doors, cowl and B pillar areas. I think most upholstery shops use 1/8" thick water resistant upholstery board (material). I have purchased this kind of material from an upholstery shop in the past. I think you can make a pattern from heavy wrapping paper and transfer it to the hardboard material. Most model A door upholstery has a padding on the hardboard, but I think CPPU's have no padding.
Rusty Nelson
