guys, I plan on getting 2 12" es12d PBX extreme's. These are the old school ones. I plan on porting the box but dont want to go over 4cu ft. I just dont think I can fit a slot port in it. I did the one on re's web site but dont know how wide I the port can be. I have seen some slot ports like 2" wide and some 6" wide. I need as little port in the box so it will not take up some much air space. Here are some spec on the woofers.

RMS Power Handling : 450 Watts
Peak Power Handling : 900 Watts
Frequency Response : 20Hz - 500Hz
Sensitivity : 89.9dB @ 1W/1M
Mounting Depth : 5.75" (133mm)
Cut-Out Diameter : 11.37" (289mm)

PARAMETERS
Fs : 29Hz
Qms : 6.1
Vas : (Liters) 76.4
Qms : 6.1
Qes : .43
Qts : .40
Nominal Imp (Ohms) : 4 ohms + 4 ohms
SPL 1w/1m (dB) : 89.9
SPL (2.83V/1m) : 95.1
X-Max (mm) one way : 9
Pe - RMS : 450 Watts
Pe - Maximum : 900 Watts