Serp, welcome. Apparently you haven't read the right stuff. In a 5.1 setup the side(not rear)surrounds are best placed a little farther back than directly to the side, to lend a little "phantom" back effect, in the absence of actual rear surrounds.

In your situation the QS8s should be mounted on the back wall about 6' up facing forward and separated as widely as possible, maybe just a few inches from the side walls.

-----------------------------------

Enjoy the music, not the equipment.