Interior fabric surfaces.
Steve, could please give me your source that states, "interior fabric surfaces were painted". I have never seen or heard of this being done.
On aircraft with wood or plywood covered fuselage surfaces the interior surfaces were painted. I have two photographs of the fuselage cross of a Pfalz D.XII, one is interior and the other exterior. The interior of the shell is painted medium grey. On the exterior around the cross is a pea green color.
I would like to know your source on this painting of the interior surface of the fabric.