I remember this room... very nice...
You shouldn't have any problems with the QS8 being high up and in the rear that way. With direct firing speakers, the "false front phenomenon" is a problem. Not so with the QS8s, because of their natural dispersion. Will the top woofer interact with the ceiling? Yes. But you won't be able to detect it. I wouldn't worry so much about aiming it at your seating position. Do what looks good in the room. The back surround speaker is mostly for ambience and the occasional pan across the back of the room. A couple of feet difference isnt' going to eb noticeable, nor is whether the speaker is aimed at the listening position.
Congrats on the near completion.
