Rich,
The explanation given to you was probably pretty close given the actual design differences. I think you have about 3" fore and aft motion, where the air pin box would never be able to move that far forward or back, but will move about 3-4" up and down.
Folks would just need to make a decision based on what is the most aggrevating type symptom they have and do thier best to get the right equipment to counteract that.
I'm sure you noticed as I did - the first thing that makes you uneasy is seeing that Monty moving separately from the truck! That first glance in the mirror will give you a pucker
