As the Axiom FAQ says, the QS seriews speakers are very versatile and are quite forgiving when it comes to placement.
"
Ideally, surround speakers should be either wall-mounted or stand-mounted to either side of the couch or primary listening area, from one to six feet higher than seated listeners' ears, and slightly forward or rearwards of the listening area if you wish. Axiom's Quadpolar surrounds are especially versatile and can yield excellent performance with stand or wall-mounting to the rear as well as at side locations."
I don't think you have a thing to worry about.
