I don't know the answer to that but theaters aren't usually 20fL but closer to 10 to 15 range. Also remember the RPs use the high gain ( extremely directive ) Fresnel lenticular screens. This allows a ton of light in one narrow viewing area both horizontally and vertically but it falls off very rapidly off axis. Go over to the rear projection forum and I'll bet an answer would come in seconds.
A forum community dedicated to home theater owners and enthusiasts. Come join the discussion about home audio/video, TVs, projectors, screens, receivers, speakers, projects, DIY’s, product reviews, accessories, classifieds, and more!