This is actually the preferred way to fire PR's and drivers as their momentum cancels each other out Anyway whoever liked the sub in a ported box, but not a PR box, do you know that a PR does the same thing as a port, but without taking up enclosure space? You can adjust the tuning of the system by either adding or removing mass to the PR or by changing box volume, which will change both PR tuning as well as enclosure size (duh). You'd want to model it if you change the box size to see if the decrease in box size gives the correct effect after you account for tuning change as well.and i would personally not fire the radiator and sub in opposite directions.