David, Larry here.

I have 7 speakers, only because my center-rear happens to consist of a pair of speakers, using separate amp channels, but playing mono via a Y-cord.

So, I have a center, main left and right, left-side, right-side, and "Lback & Rback". It's actually a 6.1 setup, not 7.1. (In all cases, we're excluding the .1 LFE from this discussion)

What you may be describing is a 7.1 logic, like the Lexicon pre-pro has, where the rear is stereo, not just the sides. In my system, the rear-center is the "bonus" channel, in a true 7.1, the sides are the "bonus" channels.

Larry
www.fineelectricco.com