Does your room have corners suitable for cornerhorn loading at one of the 15' ends?

Yes.

If so, I'd be inclined to put JBL 2241's in a π cornerhorn configuration at each corner.

Okay, so which corner horns would you recommend and why?
Also any reason for a 18" as against a 15"? Is it because the room is so large?
When i think of a 18" its huge. I have to put my bigscreen tv between the corners as well. I should have told you that before.

Thanks

Andrew