That's a lot of weight leveraged that far behind the hitch. If the camper is 48" past the end of the truck, doesn't the motorcycle carrier have to be even further out, maybe 60" to take into account the handlebars?
Have you considered carrying it on the front end?
Bill
Nodwell RN110 out moose hunting. 4-53 Detroit, Clark 5 spd, 40" wide tracks, 10:00x20 tires, 16,000# capacity, 22,000# weight. You know the mud is getting deep when it's coming in the doors.