Bedlam is spot on with the comment about overloading even with a 5500 or 550 particularly if you pull a boat like we do. That said, careful planning and budgeting your weight is a good path forward regardless. Our most recent camper is a 2017 Host Mammoth currently mounted on a radically modified F350 DRW but we're stillright at the Dana Spicer max on the rear axle. We've looked at Douglas and another local manufacturer but found Body Werks in Elkhart has the best bang for the buck.
http://www.utilitybodywerks.com/photo-gallery.html. We're inspected their work and the welds are solid as is the sheet steel work. The clincher is they are $8000 less than Douglas!