I've got an older Hallmark, 9 1/2 foot model. Many if not most of the posters here are more the minimalist, back country explorer types,(or aspire to be) and although Hallmark does make models for compact truck, (La Veta, Raton), most of their products are more full featured (heavier). True fullsized pickups have become less common, and even if an owner has a 3/4 ton truck, it's probably a crew cab, and has a lower payload than a traditional standard cab truck with a 8 foot box. Not only is payload effected, but it gets tough to keep your fore/aft center of gravity adequately ahead of the rear axle if you get your camper too heavy and/or too long. Weight and balance are double important when you take the rig off road.
I'm using a standard cab 3/4 ton Dodge, but haven't had much opportunity to go back country camping. So far the camper works well, I like the balance of a longer box truck. To me 8 foot box trucks are made for hauling cargo, short box trucks more for passengers and their stuff. The camper is almost 20 years old, and holding together pretty well. I've made a few very minor changes, and have had good service from the Hallmark factory in Colorado. They make a good product, but dang, they are expensive.