Ok i have 2 power acoustik fubr-12's and want to make a ported box for them. On their website the required size of the box is 2.2 cubic feet and the port is 4" diameter and 10.25" long. So i came up with these dimensions: 20" wide, 10.5" deep, and 18.1" tall. Does this sound good? Or do i need more space between the port and the back of the box?