rruff
Explorer
The 1794s are only Crewcab with 5.5 or 6.5' bed. Is yours the 6.5' and you plan on the 8' camper resting on the tailgate?
It is not hard to reinforce a large cab-over. The cabover area is pretty awesome for sleeping, since it only holds a mattress when you are driving, and the weight of a couple people when parked is not hard to accommodate (usually). Whether you use that for storage or sleeping, I'd strongly suggest making it as long as your cab... in which case you could easily orient the bed fore-aft making it much easier for two people to use without climbing over each other. And if you use it for storage it must be light things only just for CG reasons.
What sort of foam and thickness, and what is the fiberglass cloth and resin you plan to use?
From scaling your cutout pieces it it looks like your camper is ~71" tall, and the floor to cabover height is ~55". On my Tundra the bed floor to the top of the cab is only 44.6". Yours will be different, but I doubt more than a couple inches...? Also regarding interior height, you'll want it a couple inches taller than the tallest person who you wish to be able to comfortably walk through it.
A flatbed makes a truck very useful for truck duties! Added benefits are that you can put your entry door on the side if you wish, and you can make large storage boxes to fit underneath. Standard truck beds are stylish, but horrendous for space utilization. Another potential bonus is that when you raise the bed to clear your tires, you can gain that in sleeping berth height...
Regarding your layout, you have no place to sit inside except for the bed. And that space seems pretty restricted; tight for two people to sit with their feet on the floor. And then you will be in the way of anyone wanting to use the stove or fridge.