When I did my room, my architect contacted an acoustic engineer who suggested room dimensions of 1.6 x ceiling height by 2.6 x ceiling height. It's a great sounding room. If you narrow your planned width by just a bit, you'll be right on top of those ratios.
You might also consider 2 more subs. Check out the Swarm subwoofer array from audio kinesis for the logic behind this approach.
Good luck with your project
You might also consider 2 more subs. Check out the Swarm subwoofer array from audio kinesis for the logic behind this approach.
Good luck with your project