Maybe my thoughts are not based in what most would do, but think about it this way as an exercise for me.
If you use recliners for seating, each row needs about 7 feet from the toe of one row to the toe of the next. Four rows needs 28 feet, just for seating. The distance over which you'd ideally want to calibrate and optimize (this may be where I differ from others) becomes 21 feet. So what screen size looks good from anywhere within a 21 foot range - no seat too near or too far? (Here's a hint - it's big)
If you go with the recommendations from THX and SMPTE, as depicted in this diagram
and being as generous as the diagram allows, all the seats must fit within a range of distances 2 to 5.2 screen heights. (The range there becomes 3.2 screen heights) 21 feet translates roughly to a seven foot tall screen. If we stick with 7' tall and 1.78 ratio, the screen is 12.5' wide. This isn't outside of what you can see built here, but it's very big. 88 or so square feet needs a lot of light. 16FtL of calibrated light means about 1400 lumens with unity gain screen. That's a tough pill to swallow.
If we were a little more demanding and required a maximum of 4 screen heights, the 21 foot seating range requires a ten foot tall screen. A ten foot tall unity gain screen needs almost 3000 lumens - I don't know where you could find that.
So if the first row is 2 heights (14 feet) from the screen (to eyes) and the last row is 21 feet farther (again to eyes) - 35 feet, how much more space will you have for behind the rear seats and behind the screen?
I've not made too many allowances here to illustrate the point. This can be done, but it's not cheap to do well.Edited by HopefulFred - 5/17/13 at 6:00pm