enclosure is tuned to 45Hz...
its really too small for 12inch subs anyway, but, to tune the enclosure down to 35Hz, you will need to extend the port by about 12inches along the back wall of the box....
edit: the port is about 2.5inchs wide, correct?
extend the port along the back of the box, but make is 1.25inches wide, and extend the port till its about 1.25inches from each end/side of the box...
if that doesn't make sense to you, thats not my problem.