I see a lot of flatbeds with the garage/bulkhead that is taller than the cab of the truck. What is the reason? I would prefer it to be cab height but not sure if I'm not thinking about something.
IMO, the reason is $. It’s easier and more profitable to manufacture a “one size fits all” box height, compared with sizing the box to the model of truck cab and model of camper.
Even though a “too-tall” box presents problems such as raising the center of gravity of the rig, and increasing wind resistance (deceased fuel efficiency), a too-tall box technically “fits” and maximizes storage.
If, instead, the box height is
short relative to the cab height, the customer would understandably be unsatisfied with the loss of storage associated with the “empty space”.
The ideal situation, of course, is to have a box height that is sized for the specific truck and camper, allowing only as much clearance as is necessary between the cab-over portion of the camper, and the roof of the cab.
Spending time behind the wheel of a truck camper really helps a person understand the tradeoffs between maximizing storage space on the one hand, and negatively affecting the stability (center of gravity) & fuel efficiency on the other.