Prohibiting wave length flow is the issue with some of these boxes. If most of the wave is loading off the back door/wall w/e, then the box is extremely close to the roof it can cause cancellation. It can also choke the subs if they are fired upward.
Each vehicle, power, sub is different. Once you combine all these things, you get different results for every person. The box being tall in and of itself has almost no bearing, it is more how it loads in the vehicle it's placed.