The negative about an F550 as a dump is it will never really be able too utilized as a dumptruck unless you are hauling sand, mulch, etc. 4 tons is not very much weight. A flatbed dump will be much more versatile. You can load from the sides, fab up any sides, use it too haul job boxes etc, I could go on and on. With a 26k gvwr it will haul about 8 tons. Step it up too 33k and it will go about 10 tons payload. If you really need a dedicated dump too haul a bunch then get a tandem.