I think as long as you don't adjust the volume on the back of the sub, and use the receiver trim levels your ok.
I did the initial subs' calibration on the SVS gain dial at ~10:00 and the 3808's sub gain at 0. I ended up compensating for the sub along the opening to the dining room by dialing that sub's gain up to 12:00. After taking measurements, I adjusted the 3808's gain to +2.5dB (Audyssey took it back down to 0 and I then bumped it back to +2.5dB.) Once both subs were running together, I went for ~75-82dB total.
When you took your measurements, the seat backs were not in the way were they?
I made a makeshift tripod and the mic cleared the backs of the seats, so that should be good...
Also, if you have leather, you should throw a towel or blanket over the top, as the seats can cause reflections and skew the results.
Ugh. My couch is leather. Tell me I don't have to do this all over again.
