Placing the woofers facing the hatch will increase the amount of low end. It takes several feet for the lower frequencies to complete the "wave". I know you all have heard cars booming loud from 3 blocks and when it gets to you the bass is lessened and increases as it goes by.
With the same enclosure in my 83 280ZT my low end increased 3db on the low end of the spectrum when firing them rearward over facing forward.
The closer to a corner you can put a sub the more bass impact it has(corner loading).
"Subwoofer and Enclosure Tips 'N' Tricks
Don't go booming into parking lots, bad parts of town, or even school. ESPECIALLY don't go booming into work. You're giving theifs 8 hours of uninterrupted stealing time. It only takes seconds for them to be in and out. Those stickers that come with your subs, put them on your fish tank (or some other appropriate location in your house). You're telling them what to steal. Also, on a common sense front, don't go booming at night through little neighborhoods. That's how sound ordinances start. Don't kill the fun for all of us!
Just like speakers, subwoofers sound best in certain places. Play around with the position of your subwoofer if you have the room. Otherwise just remember subwoofers usually sound best firing rearward.
If you license plate is rattling, stick some sound deadening on the backside and that should do the trick.
Sound deadening does wonders for rattles and road noise, but it also has other benefits such as increasing your SPL and SQ!
For Fiberglass enclosures, if they are made thin, place some sound deadening on the inside, and this will usually make them a little more solid and help separate rear frequencies.
Does your subwoofer leak air where it seals at? Try using bolts with T-Nut backings. Place the t-nuts on the inside of the enclosure. This will ensure a maximum seal and hold!
Does your subwoofer enclosure still leak around the subwoofer? Place a bead of silicone on the enclosure around the subwoofer opening. Let dry before applying subwoofer."