Arctic Fox 1150 is breaking my 2016 Ford 350 dually

My 2004 f350 did that. All the weight of the camper is on the two side rails. The space on the bottom of the camper in between is not weight bearing. The truck bed was not designed to handle that long linear twin load and as a result in buckles up in the middle. Plywood helped fix my problem but it was not a perfect solution. My 2019 F350 seems to handle that weight a little better, perhaps by design...

Rick