If your MLP and sub are at least at the 2/3 of the long wall and there are a few placement options to move your sub around to try and find the best location to give the best frequency coverage at you MLP then it should work pretty well. One factor that can come into play is localisation if you set your mains X-overs to high and i'm guessing it will be a bit more challenging blending the bass in with the front sound stage, but thats "guessing" as i havent set up any of my systems that way.I know this is all subjective, but how much detriment is there in running a single sub (V1811 or Monolith THX 15, etc) behind your listening area? I don't have room for 2 subs and the size of my front wall really doesn't have room to put it up front so would need to put it behind the seating area. Room is 12x24, sub would be about 18' from front of room right behind seating. Still trying to decide what front towers and centers I want to run, curious about the sub in the back.
I've read many posts of enthusiasts that have been quite happy with this set up however many of them are more experienced than myself in fine tuning.