Long wall or short wall

Zippy,
Recommendation:
On the long wall, but the front of the woofer is at 1/2 the distance into the room. i.e. you woofer would be at 8'
Place each 5.5ft from the side walls.
Locate your seat AT the rear wall, at mid-point (11ft)
You'll have to play with the toe-in to see what sounds best...start with the drivers pointing slightly behind each year and adjust from there.
LEAN forward and BACKWARD from your seating position and notice the difference in the imaging and bass.
Adjust to taste!
This takes the side wall reflections pretty much out of the equation and also being on the rear wall (boundary) will smooth out the bass.
Give it a try while you are playing with some of the other configurations.
Anybody else ever used this config? Comments if so?
Happy Listening!

Nrchy,
Give it a try. This config pretty much takes the "room" out of the equation. I used it in a BAD room config (15' x 15' x 8') and NO room treatment. Nothing on the walls and a rug partly covering the hardwood floor. (this was just a temporary setup)
The imaging was exceptional and the soundstage was excellent. The stage would have been better if I'd had a LONGER wall than 15'. Give it a try.....it'll surprise you.
Happy Listening.