Pm IonSQL, he designed mine (15" BL) and it slams with only 1000-1200 Rms. No port noise, at all. Those dims. look fine for a 12, Obviously it depends on port area and what not, though..
I'm building it myself. It's currently in 2.5^3 at 32hz, but it has a LOT of port noise at higher volumes. When I turn it up it's not as loud as it should be, it being in a hatch should help the volume, but it doesnt seem like it.