We kept that in mind and designed the camper to fit inside the tailgate.
Have you considered a model for mid-sized pickup trucks where the buyer may wish to have more space at the expense of a bit of offroad performance?
I'm mulling some kind of slide-in or ute-tray option for my Nissan D40 Frontier crew cab long wheelbase, the model that has a bed with 73'3" from front wall to tailgate and has 44.4" between the wheel wells. I'm happy to lower the tailgate or to replace it with something specifically intended to support the weight of an overhanging camper because for me interior square footage enough for a small water-closet is very high on my list of objectives, basically second after being able to sleep two on the bed over the cab and to sleep one on one side down below.
The additional ~18" that a unit overhanging the tailgate would provide could very much be useful for upfitting the interior, especially if the unit widens-out to the width at the tailgate opening from the rear of the wheel wells to the back of the box.
My very early sketches based on an articulated/telescoping roof were along these lines:
I have revisions in mind for the popup to see what I can do that wouldn't be soft-sided and might eliminate the matryoshka doll effect that the top on this early rev has on the bottom.
Either way though, you may find some customers would be happy for the camper to stick-out of the bed of the truck if it means getting that interior volume, even for a hard-sided, fixed-roof design.