A c-channel frame is lighter than a fully-boxed frame, but softer. To a certain degree, which one you prefer is a matter of taste, but a c-frame will never be as rigid as a fully-boxed.
For the 2017 redesign, Ford is finally making the heavy-hauling Super Duty fully-boxed.
To add weight in the frame, as well as in an improved twin I-beam suspension, stronger axles, and larger brakes, weight had to be removed elsewhere. That's why the Super Duty is going the way of the Ford F-150, and embracing the power of aluminum.
Thanks to its aluminum doors and bed box, the new generation Super Duty will be as much as 350 pounds lighter than the outgoing models, even after improvements to performance components.
The result is better handling and towing over even the toughest terrain.
Check it out at Sioux Falls Ford, and test drive a new Ford truck.