I've tried, tested and measured the 12TBX32 (very similar to the 12TBX100 IIRC) in Cubo 12. Unfortunately all measurements were lost. I liked the sound best crossed @ 80-100 Hz. It could handle enormous amounts of power and go really loud for such a small cabinet. Made from Baltic birch ply the empty cabinet is just a tad heavier then the driver itself.
With the magnet inside the horn will give the deepest bass response, with the magnet in the chamber, you'll get less deep bass but a bit more extension in the higher regions. So something a bit more suited as a "kick bin" above a dedicated sub crossed at say 60 Hz. The Cubo 12, then a horn loaded 10" or 12" coming in around 140 - 150 Hz.
So for use in the house, I would use the magnet in the horn, no high pass (at low levels) or a high pass at ~25 Hz. Low pass at 60 -80 Hz. As the Cubo 12 isn't made for the deepest bass you might miss some low notes. In the house there are modifications (and might be ways of placement) possible to make it go 10 - 12 Hz lower To be honest, without those modifications I would not