We just got back from our initial 9 day "break in trip" pulling a 2013 Subaru Crosstrek (about 3200 lbs) with our 2012 Forrest River Lexington 283ts on a E450 V-10 chassies. Put a bit over 1000 miles towing thru mountains of N. Carolina and Tenn. Never had an issue with the set-up. Roadmaster Stearling bars and Blue Ox base plate, Ready Brake brake system.
Had no problem with interstate speeds, seemed to have a "sweet spot" between 60 to 65 mph on the flats running about 2600 rpm. Up grades it will rev up but it was no problem holding speed. Going down the tow-haul kicks in and you really don't have to touch the brakes. Back roads where speed limit is lower, it was a pleasure to drive. Only thing I want to do is replace the steering damper with a heavier unit like the Roadmaster.
Haven't weighed it as it's just wife and I, one dog, and we tend to travel light.
Grumpy