Try and experiment with the surrounds before you drill any holes. The QS surrounds are very accommodating to eccentric placement. They can be mounted at different heights--Dolby Labs says to the sides and slightly back, from two to 5 feet above the height of seated listeners, but every room demands its own variations. I've heard installations with QS8s very high up at the rear in a loft, and they worked wonderfully.
Get some friends or assistants to hold them in different positions and heights to see what works best while you listenn to some good movie soundtracks and good music mixes.
Axiom Resident Expert