Interesting speaker, would appear to be the theoretical cousin of the Mirage Omnipolar, or Shahinian speakers, though the rhetoric on the website would try to distance those associations.
As for the GR165X, I am sure it will hit 30Hz in a box of that size, I am not sure if you are going to try to model it exactly, or just knock off something similar. The flared nature of the enclosure (it states 21x21 at the bottom, but does shrink in footprint as it gets taller) makes it hard to guess the internal volume, but I am sure you would be able to do 1.5-2 cubic feet per driver, if you wanted a ported box (like they suggest that speaker is).
As for your question about U frame and T line, I would say it depends on the length. A U frame is usually bass only, and thus the depth is quite short, in order to keep resonance out of the frequencies that the woofer is covering - ie Martin King talks about a 16x16 panel, with 7.5 inch wings, with a resonance of loosely 200Hz+ - but this is destined to be above the woofer's passband.
A T line uses the resonance as the lowest frequency for reproduction, and tends to be much longer.
Not sure why you would want to try an OB version of this, as it is not an OB to begin with.
A T line will be tougher, I think, with that many drivers, in a relatively short distance.
In any case, what do you intend to use as the spherical deflector?
