frame flex with anti sway bar

The 2015 Ford F-150 saved about 700# by going to aluminum. It has been reported that the Super Duty 2017 models with aluminum bodies will only save about 350# because the remaining weight will be added to box the truck frame. It appears that Ford is going to stiffen the frames on their aluminum bodied Super Duty trucks. The cab and chassis version will still be "C" channel under the bed so that it is easy to attach after market beds.
There is nothing wrong with "C" channel frames, but they won't resist twisting as much. Semi Trucks still use "C" channel frames.