Run the simulator but for a single driver and set the VAS for 1/2 of the spec.
This is the best case for an isobaric.
The isobaric MUST have nearly zero leakage, both in the drivers and nil leakage in the enclosure to work best. The smaller the volume of the enclosure between the drivers, the better.
You can experiment with putting the drivers facing each other on the front. They still need to be reasonably well sealed.
Test the seal? Gently press on one, and see that the other moves the same amount, and how long it stays in that position before leaking down. Don't push in a way that offsets the cone and causes the VC to rub - equal pressure.
Now this is a driver with an Fs of about 30Hz. It's not going to work below Fs in any reasonable box. Getting NEAR Fs will require careful tweaking of the box volume, the port and the like. The best you may be able to do is to get some rise in the response before rolloff on the low end.
The Qt of 0.35 is a plus in this instance, since the driver will "try" to work in almost any reasonably sized enclosure, ported or sealed that you pick.
The problem with an amp with a "6dB" boost at 30Hz is what it does below 30Hz. Your driver will run out of excursion FAST unless there is a sharp rolloff below that boost point. Should it keep rising, then the "boost" is essentially useless in practice.
Suggest you run your simulations some more. Set the port for ~35Hz. and see what sort of box volume yields flat or slightly raised output at and above the 35Hz point.
As I said, halve the VAS and compute for a single driver - when actually building DO NOT FORGET to SUBTRACT the volume of the isobaric chamber from the total volume!! Did you do that??
_-_-bear