I have customer that does the whole eco product tradeshow display thing.
so he wants his signs back to be plywood that is made up of exposed edge. so think of 3/4" wide 8' long 3/4" plywood strips glued face to face.
the back is 96" wide 18" tall I will recommend outdoor plywood or marine ply. I was thinking of fully sealing and coating the faces and ends with epoxy to fully seal them and then a clearcoat to protect it from uv. of course all voids would need filled. I was thinking of some appleply with a outdoor glue since it really does not have any voids.