The first rule of paper or card model making is to use 3 or odd numbers of layers, for the same reason that ply wood is always made of odd numbers of layers, the layers tend to counter warping. Second rule is that you MUST seal the surfaces - shellacing was the normal method in the past, but some artists sprays should have the same effect. With those two techniques, paper models should be robust enough to have a long life where they are not directly handled.
Regards, Greg.P.
m> I was thinking the same thing but concluded that several layers of lightly