Building a JL speaker box

On JL audio's site, they have their recommended speaker box layout for the speaker I'm looking to buy:  http://mobile.jlaudio.com/products_subs_enclusure.php?series_id=15

I'm putting this in the back of a Montero Sport SUV and I'm wondering if 1) this is absolutely the best way to go design wise, 2) is there any benefit in having your speaker facing upward in a wedge type design, and 3) if I build it like the site says, do I need to do any tuning or anything?  Maybe this is already tuned for that speaker. 

I've built speaker cabs before but they were usually for DJing and sq wasn't really my main concern and I was still in high school and didn't know much about cab design (I simply got the internal volume close to the specs). Thanks for any input, I'm sure everyone else who is new to building cabs will benefit from your replies too. 

JL does a great job of showing you exactly what dimentions they suggest for building a speaker box. From what I've read, most people suggest filling the box with cotton or putting damping material behind the magnet to absorb the backwave of the speaker. I've also heard that such foaming "fools" the speaker into believing there is more space available.

I can't seem to edit my previous post so ignore the whole foaming issue below my post........I accidently pasted something I had in my clipboard and can't remove it. 

I'm putting this in the back of a Montero Sport SUV and I'm wondering if 1) this is absolutely the best way to go design wise, 2) is there any benefit in having your speaker facing upward in a wedge type design, and 3) if I build it like the site says, do I need to do any tuning or anything?  Maybe this is already tuned for that speaker. 

1.  The dimensions don't have to be identical but the internal volumes do.  The box can be built to any shape that fits the car best.

2.  No, and no detriment either.  It's a matter of fitting the box to the vehicle and/or aesthetics to design a wedge style box.

3.  The designs shown on the site account for all tuning, volumes, etc.  Read all the fine print.

This subwoofer can be used in either a sealed or vented enclosure.  Have you decided which one you want to use?  When you use the word "tuned" it implies using a vented box.  The box as shown will be properly tuned.  And as for the polyfil, I use it (in varying quantities) in all speaker enclosures.  You don't have to account for internal volume before doing so...just add or take out using your ears as your guide.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

well as to question 2, it seems to me that this would matter very much.  I mean speaker placement and resonance within a car fluctuates very much so I'd think it would matter.  Should it hit the hatchback door dead on or at an angle?  Or should it thump straight up on the ceiling?  I'd have to believe the direction would matter and the design would have to work accordingly.   

For my car, it has such a straight back area I think a normal box would do.  The only "cool" design I could think of would be to run the box long and thin so it makes a "step" from my cargo floor to the top of the back seat.  However, a lot of the air space would be to the sides of the speaker.  Maybe that's a good design, I don't know.

I'm a guitar player so most of the speaker stuff I tend to deal with is mid range freqs and open backed amps verses closed cabs.  When I say tuning, I don't mean a ported cab.  In fact, for the tightest and punchiest sound sq at a moderate level, I think sealed is definitely the way I'm going.  I guess I mean tuning in like using solid woods for your cab vs particle board or having jagged edges inside, baffles, or anything else that might make a difference.  I've heard of closed systems being tuned to their cabinets but I don't really know what that means or entails (just filling the right amount of filling?).  Maybe the speaker is simply designed to tune itself (as in design and engineering) as long as the cab volume is right and the enclosure is perfectly sealed or in a good ported boxed. 

I hope you guys understand what I'm asking.  Car stereos are still new to me and I've seen a lot that sounded like crap so I've taken the time to really learn this as I venture into my first major install for myself. 

Sure it matters how the sub is facing in the car.  That's for you to experiment with in placement, not particularly the angle built into the enclosure.  Mounting a sub horizontally, as in facing straight up, opens up another area you have to consider:  woofer sag.