Rojo, how about coosa 20 instead of the 26? I figure on getting a 4x8 sheet, and the 20 is about a $100 less money. They are both "waterproof", just that the 26 is more dense. And since the fiberglass is supposed to provide the strength, maybe the coosa 20 would be good'er nuf, dono?

And thank you for all your help.