i am building a box for 2 sundown zv4 12s on a dc5k. its going into a 2007 dodge dakota ext cab. my max dimensions for the box is 48x16x20 and i want to try a aeroport instead of a slot port. I wanted to only have port i dont want to have multiple ports , just one big one. I was thinking on the diameter 8.5 since i have the aero already made for that size just have to cut to length i want it to fire forward or up but i dont know what would be better or how to find the length to tune around 32hz i tryed box calc but they all say i need around 17 inches but i see so many people with ports that are almost liek free air but play lows. i need help