You're welcome! Correct, I used a 3.2 DF (2.5 ohms output impedance) to get the alignment, but ideally you would design around your amp's DF. ?? I mean this is what the measured specs I have calcs, and of course the big vents is what makes the Vb calc'd from the posted dims somewhat greater. Using published specs I get ~8.97 ft^3 net/~38 Hz Fb, so should still work fine in a slightly oversized/lower Fb cab.

GM