Have you considered what @drewp29 mentioned and walling off the area between the column and rear wall? 15' from the screen is plenty to have a false wall and put all of this behind the screen. Just a thought.Screen will be above.
I was just going to angle the speakers up a tickle. Or just leave.
Sitting 15' away from the speakers
The rear HT10 will be sitting on micro marty behind the coach. 2-3 '
Not perfect but kinda limited.