I'm planning to do a 140" diagonal cinemascope AT screen. I'm planning to use it with either the pannasonic 8000u or the mitsu hc7800, do I need to have an AT screen with a gain. I would like to know if I can do a DIY AT screen with a 1.4 gain. Is that possible? Thanks. I don't want to go into the details of the building because I'm couple of month away from my ht build where I start building the screen.