That box is so ridiculously huge. It's basically a wall at that point. The port is literally right behind the driver's head.
You guys see why the front chamber port exit had to be pushed down lower than the top of the box? It's because of how close it was to the top of the cab plus how big the port is and how much power this whole setup is using or can use (8500w lol). I'm so glad to see this one put together, I spent a very long time on it. All the angles and the depth changes and the limited space, plus the fact that this is a 6th order for a giant soundqubed 4" coiled 18, made this a challenge. The right side of the box is removable so he can pull the sub out, if he ever blows it with all that power.
I don't think there's a whole lot of boxes out there that look like that one above does.