I can't believe I am the only one doing this, but must be. I want mine on the roof, but I am waiting for rack, so for now, my 48" is mounted behind the second row of seats on my 4dr. xj. Just put the base against the inside of fender well on drivers side, (the top piece has to have the bite bar at a 90 degree angle) the top will lie on top of the passenger fender well. It holds tight to back of seat, which is angled so it really doesn't take up to much cargo area, but can be a pain to get out if packed to hilt. I bungie top to seat latch in case of roll over, base will stay under tire. In front end collision, it would be perfect spot.
As a side note, I don't like it inside as if you ever use your jack, it gets muddy. C'mon, they are only 50 bucks to begin with, and it will outlast my kids life anyway.
Jason