George get a taller box 7ft or more, one you can stand up in and utilize some of the space better. You'll find it's not that much different driving around unless al your work is near low branches.
I am 5' 9 and the only problem I had with my old vortex was hitting my head on the roll up door track...aside from that there was never a problem moving around in there....that box look shorter then a vortex box.....