At first you said to tune fairly low, but then you stated to tune around 42hz. My thoughts were to make it 2.5-2.9 and tune about 33hz. The fs is 32. I'll just aero port it and play with the tuning, but the size has me a little baffled
The response drops off very high, but has a big hump at 42 Hz. That is why I suggested tuning. I know it doesn't seem low, but it's a 12" SPL sub, and an f3 = 35 Hz, I'd say it's not half bad.
The good news is that with T/S specs like this, you can use classical vented alignments, and get excellent transients. I'll try to cook some up, in my free time. Work calls though.