ported or sealed for spl

ported

The current though on woofers in a hatch back is to point them back and up at the glass/hatch.  You could say that the shape of the hatch acts like a horn. Its like pointing a home sub-woof in the corner of the room.

Port cross sectional shape has no real effect.

so your saying to piont the port up wards to the window?

the woofers and the ports ...if you use ports. Ports do not nessisarily make a woofer louder.  What they do is extend the woofers ability to produce lower octives. The port takes over the work of the woofer as the frequency approches the tune of the port. So in effect it does make the woofer louder but at the lower frequencies. This does not mean that it is louder in its over all responce. If you design the responce to peak at this point to an extrem then you end up with what is refered to as one note wonder, which is loud but does not usually sound very good.

If your only goal is to get loud then you want to build a woofer/ box combo that will give you a peak responce at the resinance frequincy of the interior of the car.