I want these speakers now. A 6.5 with a 35 Fs is my kind of 6.5. Man, you could do a t-line @ 33 hz.
See, my thoughts are that with a ported box, your sub is wasting energy pressurizing the chamber. It doesn't need loading. So, with a t-line, all of your power will go into cone movement. You face a major restriction when that loading chamber air tries to get out of that port, and a t-line, there's not loading like there is in a ported, so the woofer would be free to move. It's got a hair over 11mm of xmax, which is pretty good I think for a speaker that small. T-line means all of the woofer movement isn't restricted and the rear wave is unobstructed and unaltered, besides flipping the phase. There's an effinciency factor to your system when the subs doesn't have to force the loading chamber air through a port restriction.