[sergmx]

Your best bet will be to get a slim sub with a slim box, and just place it to the side, or maybe if it's small enough under the driver or passengers seat if you care about your trunk space. I still have my 2 10's from my old car just chilling in the living room since the box takes up the entire back area of my hatch. ORR you could try and make yourself a custom box, placing it to the side walls of the back area!

 

[sergmx]

Ive seen it done on other cars, and thats also another option for sure. I just wouldnt do that myself, because if I ever got a flat tire in the middle of nowhere, I would def want to make sure I had the spare tire.