Great to hear that the cornerhorns would be feasible in the space. If you look at the plan carefully you will see a corner molding trim in the front of the proscenium/stage where I was planning on placing the cornerhorns. Hopefully that is where you thought I would be placing them. While the side walls of the room are relatively unobstructed, I am unsure as to how the acoustics would be affected by the opening for the screen. There is a short wall just behind that area where the cornerhorn would be, but towards the middle of the room, it opens up where the screen is. Will this be a problem?
I can likely soffit mount a 4pi in the middle of the speaker wall for the center channel.
I will then use a big summed mono sub up front and two summed mono reinforcement subs in the back to help with lower bass modal dips.