I have a 5.1 setup with future expansion for 7.1.
At that time, i would have about 6" to 1' of horizontal displacement between the listening position and the rear speakers. I plan on putting the speakers up a bit and turning down the calibration 1 or 2dB below even level with the other speakers to compensate.
My initial testing is showing great promise so far.

"Those who preach the myths of audio are ignorant of truth."