i have four MA121XQ subs that I want to build a ported enclosure for. The manual recommends 3 cu ft. for one sub so am I correct in assuming that i need an enclosure with 12 cu ft ? Also it recommends 25 sq/in. port area and port length of 14 inches so does this mean i could do 1 port that has 100 sq/in of port area. i am a little confused because when i punch all of my measurements into the Torres box tuning calculator i have to use different dimensions for the port to tune to 35Hz. These are the outer dimensions that i have and will be using 3/4 mdf

Height 23"
width 36"
depth 32"

Port dimesions

Height 20"
Width 5"
Lenght 9"
This will be in a full size K5 Blazer if that matters at all . Any help you guys could give would be greatly appreciated.