[brucepick]

I saw some white plastic sheets at Home Depot but they were far heavier than good ol' coroplast, and not as stiff if I recall. As much as I keep trying to find alternatives to coroplast, it usually wins out.

I do like using 2.7 mm lauan plywood, primed with exterior house paint - thin the paint some so it doesn't go on in gobs. Stiffer, but heavier than coroplast, and surprisingly weather resistant if primed. Haven't tried it unprimed. About $10-12 for a 4 x 8 sheet at HD etc.