I have a lot better success in making 1 single run with the port if i side fire rather then fire back.

I prefer not to have to bend the port(s) is why i am asking if there is anything "off" sounding to this.

My max square dimensions in cargo area is - (for this height)

42" wide x 12" high x 24.25" deep.

If i were leave a 7" gap in the width to allow air to escape out of the box and shoot up towards the car, i would then have-

35" wide x 12" high x 24.25" deep.

At the very back of the box on the side, i would, for example, have a 10.5" high x 4" wide port.

I'm assuming i should have it as far back in the car as possible when side firing.

If i choose to side fire, should i make the box as far deep as possible? Meaning make it the whole 24.25" deep so i can fill in the remaining cargo volume as best as possible?

subs are facing up by the way.

What vehicle?

If it helps, one of the best street A guys in the world runs a single massive sewer pipe port rearward with one ten forward facing and one drivers side facing. That is in a CRX.