Alright, the boxes will be the right size. You say the bass is omni-directional, but most guides recommend firing towards the rear of the car. With near-taillight setup I had in mind they would be firing towards the cab, but at intersecting angles. I'm thinking against this idea.
The spare-well setup was by preferred, but it would be firing directly at the trunk lid, and rattling trunks is one reason it's took me this long to even consider buying subs.
So now I'm leaning towards putting separate boxes on either side of the pass through hatch. Now I know you said they were omnidirectional, but I think for my uses at least there's things to consider. If I fire them towards the seats, this keeps the subs safe and my trunk useable without worry of something sliding around and puncturing a cone, but it goes against what I've read for every setup other than a truck, and if I'm not mistaken the subs need a certain amount of space in front of the cone as well, which this wouldn't give.
If I fire them upwards, I'm thinking I could get a louder, clearer sound because of the open space next to the 6x9's, and keep the subs protected from trunk junk as well. But will firing upwards here still rattle the trunk, even though it's mostly under the rear glass? Do I want the subs firing into the cab, or is it better for them to be firing away? Also, if I get a rear STB, how is it going to interfere with the subs sitting directly beneath it?

If all else fails I can just go with by the book rear-facing boxes, but I'm kind of trying to avoid that- mostly so I can throw $h!t in my trunk and not worry about it, but also because I like to be a little creative- but not fcuk something up in the process; hence asking you guys for suggestions


EDIT: Damn, I type too much!