F150 bed rail weight limit?

I have a 2008 f150 with a 5.5ft bed and was wondering if anyone knew the weight capacity of the bed rails. I made a lumber rack that attaches to the tops of the bed rails and plan on putting a lot of lumber and steel on top of it, maybe up to 1000-1500lbs. I know the payload is about 1600lbs but I just want to make sure the bed rails can handle that kind of weight, especially with some lateral force since I’m planning on making a sort of crane that attaches to the rack and swivels to pick up heavy items like logs and engines and put them in the bed. Most of the items would likely be under 1000lbs. Would it be able to handle it? If not what’s the limit