Here's my idea - let me know if you see any obvious flaws! Harkness hall can supply screen material with hemmed sides and velcro fitted. So, my idea is to get an appropriately sized rectangle and fix it straight to my wall with those adhesive velcro strips you can buy. Total cost for a 90" 16:9 high contrast grey screen should be about £120. Sounds like a bargain to me, and alot simpler than building a frame, but do you think it will work? How much tension does screen material typically need to eliminate ripples? I guess this will depend on the elasticity of the material - the less elastic the material, the more tension it will need.