2 FI 12" Q's sub enclosure

[Dodge504ram]

i have 2 12" FI Q subs which are dual 1 ohm, 2 audiopipe AP-15001-D amps, a Tsunami 20 farad cap .. im wanting to know what size enclosure would be best for the subs .. i have a 2005 dodge ram which i cut out the center console and will be building a box that will flow from the 4x4 shifter to up an over the back seat .. i prefer the box to be ported so i was figuring about 5 cubic feet but wanted to get some other opinions