Aero Port help

[the727kid 1]

Alright, I want to switch to Aeros from my slot port to give my subs some more airpsace (2 15s with 5.5cubes is a little small for me).. anyways could anyone help me out here, I know how to design a slot port but not a aero port. How many would I need to get proper port area and the length for say 31-32hz? Box is 38.25wx16hx24.5d

[danssoslow 0]

http://www.psp-inc.com/

There's a port length calculator there.