Honestly, everytime I install amp/sub in a hatchback car, they face the tailgate. I can't tell much of a difference between facing straight up or firing at the tail lights. Either way, you're still using the hatch area as reverb. and it's moving air the same.

And unless you build a custom floor, aka spare tire enclosure, I think the tail light facing sub box takes up less cargo room and looks better IMO.

Notsafe Motorsports