I don't have a solid answer for your question on surround speaker placement height as I am still trying to fiddle with my setup as well. I have a 6.1 setup (633T LR, 634VAC, 534SS for side and rear). I have the rear middle on a wall mount near the ceiling (8' ceiling). I think I might replace that with a ceiling mount as I can't point it down as far as I'd like. BUT, I don't know if I should be trying to point it down further.
The sides are pointed to ear level from the ceiling immediately to my sides (about 9-10' away on either side). They are in dipole mode. I feel like there's a decent ambient sound field being generated but I can't help but feel like it's slightly to the front of me instead of truly wrapping around me.
I had thought about getting a ceiling mount for the rear and pointing it down more like the sides to see if that made a difference. But yesterday someone posted on my AVS thread that they thought they should be pointing up more (the sides) and so now I'm completely confused.
I think I'll experiment a bit (I hate to do that because I'm trying to finish my room and this will take at least an hour or more). Or maybe I'll just wait until the new year.
Heh, guess I really haven't helped you after all. Sorry about that. Okay, to anyone else out there that has mounted their 534-SS surrounds up high, feel free to chime in with your experience.
Thanks,
Mike