Budget setup- JBL GTO 12's-Need help with enclosure design

So I'm good at building enclosures.....calculating ported enclosures?  Not so much.  I've just bought a new tow vehicle and using some budget equipment to put a nice setup in it.  These are new items I've had laying around to put into a project car I'm building that won't be finished for a while. 

Vehicle : 2004 Escalade ESV (Suburban sized one)

Location in the vehicle: Rear hatch, against the 3rd row.  Want to keep some cargo room

Space available (Length x Width x Height): 46" wide is set.  16" deep is set.  The height is my variable.  20" is maximum.  All dimensions are internal.

 
Subwoofer make and model: Subwoofers are JBL GTO  4 ohm models

Subwoofer Size: 12"

Number of Subwoofers: 4

Type of Port (Kerfed, Slot, Aero, etc.): any but prefer slotted  (Subs up, port back.  Box against the 3rd row seat to leave room for cargo against the hatch)

What type of music do you like?: Rap BUT I hate the rattle trap boom that most rap fans like. 

Is your goal SPL or Everyday Music?: Everyday music

Tuning Freq (Hz): 30

Volume : ? 

Questions:  So, recommended enclosures from JBL are 1.75 cuft.  This INCLUDES driver and port displacement.  The recommended port is 4" round x 10" long which tunes it to 34 hz. My questions are:  Has anyone built a ported enclosure for these subs? If so what was your size/results?  If I go with recommended enlosure, how to I go about doing the port?  I'd rather do a single port, not 4 individuals.  Any suggestions?

P.S.  Subs will be on 1800W for all 4.

Thanks in advance