When I loaded my Hallmark Guanella camper on my 2021 F350 crew cab, I had only 3/4” clearance between the top of the cab and the camper. Matt at Hallmark said to add a spacer under the camper, so I added a 1.5” piece of foam. I’m wondering how much trucks really flex. Now my truck is long being a crew with an 8’ box. I have no intentions of going rock crawling. Is there a way to measure flex? I don’t like the look of the camper on the truck. The camper is 3” above the top of the bed side rails. I know it is recommended to have 3” above the cab but is that always necessary?