Actually the ideal room also requires careful consideration for room acoustics as well.
For example, a room's length should never be greater than 3x times the height, which is why you see room ratios like 1.0:1.6:2.3.
Then you still have to take the screen height saeating distance into account...
OK Mark, we are getting closer....
So if the maximum room height is 8' (2.45m),
the maximum room depth should be 8'x3=24' (7.3m),
the maximum screen width 24'/3.68x2.37= 15.5' (4.7m)
the corresponding screen height (at 2.37:1 projection) 6.5' (2.0m)
I then would put the screen 1.5' up from the floor.
At a viewing height of 3.5' (eye level) I will be at about 1/3 of the screen height.
Believe that's OK?
What do you think?