I can pull the EC out far enough to accommodate about anything, but I may have problems with WAF if I bring it out much. So, to answer you question, I can probably stand a box sub of approximately 15” X 18” fairly easy. This would place the sub about 3” from the EC and 3” from one wall (with about two feet to the opposite edge of the EC, but since it is not quite perpendicular to the apex of the corner, the usable space is nil. The sub would be very near the wall it is parallel to. I don’t know how to create and link a lay out of the room.
Thanks,
TW