Yeah, it's certainly more tuned to sealed use (really low Fs and EBP = 55 << 100). It also has a pretty good frequency range, up to about 4k and down to 50Hz at -3dB in a 1.5cf box. It looks like it'd be really wonky in a ported box, as you've found.
The trade off comes with the efficiency. It's not going to get super loud and the power handling is modest. With the rubber surround and lower efficiency, I'm thinking it's meant for consumer applications, like home stereo, etc. and not pro-audio. Or kind of somewhere in between. But they will certainly be worth trying out if you've got them.
If you build a box 29" tall x 18" wide x 16" deep outside dimensions with 3/4" ply and the baffle inset 1" (inside dimensions: 27-1/2" x 17-1/2" x 12-1/2"), you'll be right at 3cf net, which looks to be a good starting point. It'll weigh about 50 lbs. If you use 1/2" ply, it'll be closer to 40 lbs. (Don't forget to make it 1/2" smaller on all sides if you do).
The frequency response looks pretty good to. Fairly flat with a slight bump at 2.5k and slight dip in the mids. Should sound pretty nice.
