Nick,
Everyone is different, and there is no ONE best position. To be honest some people like the left/right surrounds slightly in front versus behind, or directly to the sides.
Keep in mind these are not direct radiating speakers, so when mounted directly to the side, the tweeters are directing sound behind and in front of you. If you have them to far back, the rear tweeter is not helping the experience and conflicting with the rear Qs8's in a 7.1 setup.
A lot depends on your room. Most importantly you need to experiment with differenct locations. Don't take our word for it, use what sounds best to you.
