Newbie here. I am going to make my own screen for home theatre with an NEC LT155 as the projector. Given that I can only mount the projector within a small ceiling area because of the room size and layout, I suspect the screen size should be based on what the projector displays on the wall, which is 85"x39" approxiamately from an initial screening with 'A Bug's Life' in widescreen mode. Should I get the projector permanently mounted and then determine the exact screen size from this? Should the border be just outside the edge of the image or straddle it? Finally, can I safely assume that all 16:9 movies will fall into this same border area? I can't imagine they differ or no border would be 100% correct. Thank you.