I am moving into the design stage of the 4th order for the crew cab. I have hundreds of boxes under my belt, but only a few 4th orders. I made a few that did well in open cab style jeep installs for what it was. I used winISD. Im leaning more to the cone area style build then software. 2 12s with a sealed side about 2.25 and 2 or 3 times that for ported to 45ish hz. I would play with some designs and run them in my burban but I feel the cabs will be a huge difference on output. I have tried to look for data to help get more inside, but I haven't done well of getting what I am looking for.