Thanks to both of you for helping out!
I can just about manage 12 feet lens to screen if PJ is mounted on rear wall.
I do not aim for CIH or 3D, just a simple but good setup, and main reason to look at PJs is the fairly small size of TV screens.
The room will not be very bright, PJ will be used mainly in the evenings for movies, and I plan to use a TV for any casual or daytime viewing.
As for lens shift and rainbows, I really don't know what these terms are, I need to...