Parallel tuned 6th order

[afanofdeftones]

Hey guys. I was wondering if anyone knows and can explain the fundamentals of designing a parallel tuned 6th order. I have a solid understanding of how to design series tuned 6th orders but I feel the same principles used to design a series tuned 6th may not translate to designing a parallel tuned 6th. I did some researching and came across some information but nothing solid enough to begin creating a design so I figured I would ask here. The design is going to be for a 15" dual 2 ohm Fi SSD, ran in series seeing 1,000 rms. I have 10 + cubic feet of room to work with. The enclosure will be going behind the seats of a hatchback, firing towards the trunk, unloading off the rear of the car. The design I came up with for the series tuned 6th is 4 cubes @ 28 Hz and 6 cubes @ 56 Hz. My output goals are more focused on low end output, more so than getting as loud as possible, while still keeping this a daily set up. I wasn't sure if a parallel tuned 6th may help me better reach my output goals since the lower chamber would be firing into the car rather than inside the enclosure. Information I am unsure of with designing a parallel tuned 6th is how much port area I should go with for each chamber, how large (or small) I should make each chamber and what tunings I should (or could) use. I know with a series tuned 6th its ideal to keep tuning one octave apart. Not sure on the parallel designs. All things possible I'd like to effectively cover 26-28 Hz to ~60 Hz, but I know enclosures are all about trade off so I'm willing to sacrifice here or there to meet specific goals. Thanks guys, any help is appreciated.