States can have a vehicle length law on the books and same for a combination max length. My state is 42' for a RV and 68' for a combination.
I've yet to hear of anyone (rv folks) being pulled over for being over either max lengths.
A '17 F350 DRW has a 9900 rawr that will carry all the hitch load and other gear in the bed. Many owners report around 3500 lb unladin rear axle weight (actaul weight depends on scaled axle weights). This leaves approx 6k-6.5k lbs for a in the bed payload. Your gonna' have close to a max loaded truck.
Just for fodder.....Next truck up is the F450 cab/chassis with those big 11.5k-12k rawr numbers which will give you plenty of reserve load carrying capacity.
