I am currently determining how far away to mount the projector from the screen. I am looking to have the projector be 11'6" from the screen but can be moved up as close as 10' and as far back as 15'. From looking at the calculators this is too bright for a 106" and just about right for a 120" screen. My seating distance from the screen will be 12'. I think a 120" screen may be a bit too much that close. Ceiling height is 9'.
It seems from the calculators that 22fL seems to be a good brightness. My room has some light during day but is completely dark at night. Walls are asphalt gray but ceiling and wall opposite of screen is a khaki color. I am unable to paint the ceiling or wall opposite screen.
120" would be perfect at 12' imho. I am at 106" at 10ft viewing distance and it's just right. Glad I didn't go with the recommended 92".