Just remember, port area has nothing to do with box volume and everything to do with driver displacement. If you are running designs and see an increase in output when you change port area (especially making it smaller) it is because you are manipulating something else unintentionaly. When you make a box smaller you make it less efficient, 100% of the time. It isn't that the driver likes the smaller box better, it is that you have lowered system efficiency with the by product of increased mechanical power handling. It will never be as loud as a larger more efficent box with proportionaly less power due to thermal compression. If you are modeling, shoot for lowest vent velocity possible while keeping you port a managable size, that really is all there is too it. It has nothing to do with the volume of your box...