I believe that would be a good plan...
The total external space from the external wall to the beam is around 30'x12'. Accounting for the bathroom, walls, studs, drywall, etc. will leave about 25'x11'. That is a nice layout to work with, even with space behind a screen if needed.
The other beam (15' from the front basement wall) would be a nice place for projector placement. From that distance most of the projectors will do anything from 90" to 120".
Even if you leave space for floor standing speakers, around 9' width will be left for the screen - good enough for 120" screen. I'd go with 100" or so max.
Diogen.
THANKS for that advice.
I would be more than happy with 100." Considering I am watching a 34" CRT right now Speaking of which, I am selling it. While I love the PQ on it, the beast weights 220 lbs. And I do not want to get it to Illinois. I will replace it with a 40ish inch LCD panel.