Vas=5.33 cu ft
Fts=21Hz
Qts=0.39

So PiAlign equivalents are:

Vad=5.33
Frd=21Hz
Qd=2.56

PiAlign recommends a 2 cubic foot cabinet tuned to 20Hz using either a cylindrical 5" long, 1 5/8" diameter port or a rectangular 1" x 2" x 5" long port.

You can grab a copy of BoxPlot on the Pi Speakers website to show the response of this cabinet using Thiele/Small analysis. The box you've proposed is about 5 cubic feet, and I suspect that will work just fine. The driver will probably work very well in cabinets from 1.5 cubic feet to 6 cubic feet or so, tuned to 20Hz. You can use BoxPlot to find an alignment that will give acceptable response in this size cabinet.