Personally I think vaulted ceilings are better. The further you can get from multiple parallel surfaces, the better.
I’d say 4 ft. back is too close for rear speakers. It will be extremely difficult not to localize them. In addition, at that close distance, you’ll only hear the one closest to you.
Eleven ft. from a 120” screen? I expect this is going to end up being like an IMAX, where the screen is so big you can only hone in on a portion of it, not the entire thing (as you’d have with a smaller screen). I personally don’t like that.
Regards,
Wayne A. Pflughaupt