It would be nice if he could do it, I'm on the fence about the SI's as it is. Not having to build a box in this cold weather would be nice abd would sway ne to get the SI 18. Living close to Chicago, so we haven't had the best box building weather here in Illinois.
I did model them, in winisd. The ultimax seems to be going lower according to winisd, but not by much.99% of the time it is better in opposite corners, but not in this room. Huge bump at 40hz. It took me few days to find the best spot.