I'm using a Fi XV3 12' woofer in a 2.5ft3 net ported box....not built yet. Since this driver will be seen I wanted to keep it symmetrical and have a port on either side of it and I want to use 2" ports. I've looked a few different websites and found different results when I plugged these numbers into the equation. It looks to be between 5.59 and 6.8 inches is what I have found per port. Also I'm not sure how to subtract out port volume, again finding different numbers. I can only assume I take the volume of the cylinder and subtract that from the box volume? lastly what is end correction factor, I saw that and have no idea what that is? I'm not using a flared port, just pvc, but I would if I can figure out the math for it.