Got it! I believe the rule is a 30% to 50% decrease in port area. As you should know, port length is a function of net volume, port area, and tuning frequency. Assuming that net volume and desired tuning frequency are constant, a decrease in port area results in a decrease in port length. This is where the smaller box sizes come in because the non flared port has more port area which translates to more length so it displaces more. The flared port on the other hand has less port area which translates to less length so it displaces less! So smaller overall box with the flared port. (Keep in mind i didn't say aero port because it is only due to the flare.. nothing special in the plastic although the smooth plastic should make the air flow more easily.. The difference in air flow over plastic and mdf should be minuscule; therefore, it doesn't matter. The flare is the key!) Make sense? yes it actually does thank you. so how do i know how many aero ports to use?? is there anything that helps you determine that.