Designing a box for 2 L5

I need help in designing a slot ported box for two Kicker SDL5 15 inch Solobarics. I want the two subs in a box with one slot port in the middle. I have a 1986 Dodge Ramcharger and I have the following area to work with in the back of my truck.

Those dimentions are as followed:
1) 22 inches in height
2) 46 inches in width
3) 40 inches in depth

I can't remember how to do the formula for cubic inches or cubic feet for that matter but I think it goes

22 X 33 X 44 / 1728 = 18.48 cubic feet I believe.
This is a sketch of what I want to do. Please feel free to help me out cause this will be my second attempt on creating a monster system and so far I've spent about 1500 just on the subs and the amp alone, so this time I wanna make sure my system comes out right.

Again I would really appreciate any advise anyone in here can give me. I plan on having my system in by the 4th of July. So time is of the essence.

P.S.--> to give ya a breakdown of the system that's gonna be in my truck on the 4th of July.

 I'll be running a pair of 6X9 4 way kenwoods in the door, 6X9 2 way Memphis Audio  on each side of the back seat, powered by a Boss America 4 channel amp rated at 640 watts peak, so I'm guessing I'm running between 35-80 rms to each of the 6X9's.  My head is a Pioneer 4100 soon to be Pioneer 6400. Hell I'm even gonna change the 6X9 in the doors to a set of Cyrstal audio 2 way component set with 1 inch soft dom tweeter and a 7 inch midbass driver.  For my low end I'll be running 1 Lighting Audio Storm S1000.1 D mono amp to 2 Kicker Solobaric L5 15 inch subs.  I'm also upgrading my alternator to 150 amps and I'm gonna run 2 gauge wire from the battery to back of the truck and then split the wire from 2 to two 4 gauge wire for the two amps.

So if anyone has a set up similar to mines or any advise please let me know. thanks.

Oh yeah one more thing.  I want the box to have a volume between 8 -8.5 cubic feet.  Sorry I forgot to mention that in the other post. Thanks again

Pervy

Recommended Vented Box Volume: The vented enclosures incorporate large slot-loaded ports with ultra low air velocity and hard-hitting bass. These are not your traditional port tubes; the slot-loaded ports are integrated into the enclosure design. Compact enclosures have increased bass efficiency over a sealed enclosure, yet can still fit in tight applications. Street Bass is a medium sized enclosure that will kick out bass that can be heard from blocks away. SPL/Deep Bass is a large enclosure with high efficiency that will deliver the output needed to win SPL contests and produce the bass that goes down to the lowest frequencies.

• Compact: 3.00 cu/ft; 2.5"x16.25" port opening; 19.5" port length; each coil can handle up to 500 watts RMS (1000 watts peak)
• Street Bass: 4.5 cu/ft; 3"x16.25" port opening; 14.75" port length; each coil can handle up to 500 watts RMS (1000 watts peak)
• SPL/Deep Bass: 6.0 cu/ft; 3.5"x16.25" port opening; 13.75" port length; each coil can handle up to 500 watts RMS (1000 watts peak)

Note: The power handling specifications listed with the vented enclosure recommendations apply only when a 25Hz, 24dB/octave subsonic filter (sold separately) is used with this woofer. If a subsonic filter is not used, the power rating will decrease and excessive port noise can occur. 

Cutout: The woofer will not mount in a standard enclosure with a round cutout. Instead, the woofer must be mounted in an enclosure with a 13.75"x13.75" square opening.

Okay guys how does this sound

The box will be 36 inches in width, 20 inches in height, and 24 inches in depth.  With the middle slot port at about 4inches wide, 16 inches in width, and about 16 inches deep?

Is that okay for those L5????????

Anyone else in here have any idea on what I should do to create the perfect slot ported box for these subs? I know that 12volt and Velocity have some opinions or ideas about my design. Just let me know

HELP!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!