I came up with this the other day and posted it on SMD, I figured I should post it here too.  Hopefully someone will find it useful. I'm sure most people here have come across the "12-16 sq in of port area per cube" guideline for slot ports and the "9-12 sq in per cube" for aeros.  The problem with both of these is they only consider box volume.  Both input power and tuning frequency, along with box volume, have a great effect on how much port area you need.  This is why I've been recommend