From your description it sounds as if the side surrounds are pretty much "beside" the listening position rather than "beside and slightly behind", is that correct ? My understanding (which could be out of date) that even in a 7.1 system you want the "side" surrounds to be a bit behind the listener if possible.
My side QS8s are about two feet behind the primary seating area, about twelve feet to either side, and at about six feet off of the floor (I have an eight foot ceiling height). My rear QS8s are on the back wall about fifteen feet behind the seating area, each spaced about six feet from center (about twelve feet apart).
I love how the QS8s are able to disperse the the sounds. I had considered a pair of direct radiating speakers for the rear channel, but it was a toss-up given the space/distance. My area is about 800sq feet, slightly "L" shaped with the extended area along the back wall covering a fitness area, and kitchenette/hallway with bathroom access.
