Not sure how the vert works for them. I am assuming that since they label it a catering rig that the vert is just for keeping things warm, which I am sure that it does. The rest of the design works great. It may be that the smoke has to go all the way to the left, then half way up the chamber before coming back accross the meat.
I like my reverse flow for keeping even temps accross the horizontal chamber, and have always wondered how it would be to add a vert above the firebox with the stacks above that.