yeah its not at 13.3mm xmax. i got my port area from bass box 6 pro. it was much higher of an area than i would have imagined for a sub of its type all by itself. back in the day i used to run single subs like this one like the cerwin vega vega series 12 with just a 4" PVC pipe from the hardware store and while they did have port noise flaring the port did solve most of that so i'm pretty sure one of these 4" aero's will do an even better job for me.
thanks guys for the info and links.