Found em. Is this current? (minus screen.)
Seems ideal for baffle mount situation. Fill void completely with Roxul comfortboard (not batt) from home depot eg. and mount VP160 Flush with face of insulation. Fill all around and cavity entirely. Think bags go for 75$ or so these days.
Diffusion possible but would need to build a false wall with stretched cloth to carry your screen between stone outcropping. Lots of work but a cool mission.
Other improvements could be inverting your L/R channels and dropping your screen a bit. Sitting in front row should be priority for that screen size and sound setup. Dont compromise the entire setup for flex seating.
I like your room. Nice job.
