I would compare your total proposed load (trailer tongue weight, ATV,
and pickup passengers)with the gvw of your F-150. You will then know if you have any weight to spare for a cross the bed rack. I built a rack for my 2000 short bed Silverado extra cab that ran a ramp over the cab so I could load my grizzly on it (it was about a 45 degree angle and scared the heck out of me to drive the quad on and off) and pull my trailer. The ramp was made out of .062 wall square tubing a only weighed about 100# but I still was overloaded by about 500# when I was ready to go camping. Most 1/2 tons are severely limited when it comes to GVW.
Good luck and happy camping,
ArizAl