Did that with my current camper and a short box Ranger when I first got the camper. Had to keep the tailgate on, and the tie downs for the rear angled foreward. As for brake lights, unless the ones on the truck are covered, you shouldn't have a problem with people seeing them from behind. Only issue I had was if you got too close you couldn't read the license plate, but from a normal 1 + car length away it could be read easily.
Only thing to watch is the center of Gravity, as the COG has to be over the rear axle or else it can cause understeering due to the rear axle acting like a fulcrum, and the weight balance would be lessened on the front, which the vehicle relies on for steering purposes.
Shouldn't be an issue, just watch the weights and balance points.