Is an in-wall infinite baffle an option? If you're renting, probably not. And I'm not sure it makes good sense for an experiment either. But I do think they would work well in an infinite baffle, essentially a huge box. Trouble with that is two-fold, one is you must cut a hole in a wall or ceiling and the other is you really need to model the room or do some measurements to know where to place them. It would suck to cut holes first and then find out where you placed 'em caused huge room modes.

Might be best to sell 'em and get subwoofers that work well in smaller boxes. If you could get a pair of small subs, you could place them strategically to blend with the bass of the four π's to smooth room modes. That's the ticket, 'cause it gives you a deep bass foundation and smooths room modes at the same time.