I understand that things are almost always "build, test, tear down, build, test; nothing works the same for everyone," but I'm wondering what others' experiences are with sub and port placement/alignment in a small Suv?

1) Would it be better to have the port rear firing into the hatch; or have the port firing up, parallel to and right up against the hatch? Assuming both enclosures take up the entire cargo area just under the window line and same external dimensions. Thinking that firing into the hatch would create more unwanted rattle, which could possibly hurt output(not to mention, sound like ass)?

2) Slot port running the width of the box, along the floor, vs a square or round port, centered? Why?

3) Would it make any noticable difference having the subs closer to the front or rear of the vehicle, in either port configuration in (1)? I would think they would load better closer to the rear hatch, granting more spl?

I have a small SUV : a MAzda CX-5.

I have port firing back, on the (driver) side of the box. It's my second box like that.

When I managed to pull the box onto the rear seats, to leave much more room between the port and the hatch, the sound was better : more output, more lows,...

But you're right : the more output, the more rattles on the hatch, or anywhere in the car !  It's a never ending story !