I just read the entire thread on this project, and I think is fantastic. I have a couple of questions in regards to the loudspeakers.
After so much time and effort on researching them:
1-Why the front speaker horns were not located at 5/8 the screen height?
2-Why not spec a baffle wall? That was probably one of the problems with the piano brand; the other problem could have been the distance between loudspeaker and screen.
3-The Surround Back speakers horn orientation is wrong. The manufacturer could have easily reoriented it in order to meet space restrictions.
4-Last but certainly not least, the most important component of the entire project, the Room, room acoustics is not voodoo, is physics and again it can make or break the entire experience.
I look forward to your reply and future projects.