We just moved into a new house with a large front yard and some big oak trees. We're going to set up a graveyard and pumpkin patch and would like to stretch a rear projection screen between two of the oak trees to create a background of spirits rising from the cemetery and pumpkin patch. The screen will be 40' wide by about 10' high. We'll use a 2-foot high picket fence across the rear of the cemetery, so we can actually get away with an 8' high screen. The current plan is to hang it from aircraft cable stretched between the two trees and rear project from one or two windows in our garage. My question is: What material would you recommend for a screen this large? Thanks.