Anyone running with 5.5" bed rail clearance?

I have a quick obervation. I had a 2013 F150 CC with 6.5' bed. I purchased my first 5th wheel. I know, I know I am one of those who fell for the 1/2 ton can handle this unit. Anyway, I just bought a F350 CC with the 6.9 bed. I also have the 6.7 PSD. Now my measurements from the 1/2 ton were ground to floor of bed was 34.5" and the height of the box was 22.5" which gave me 57" to the bed rail. I had 6" of clearance to 5 th wheel. Now new 1 ton has 37.9" from ground to floor of box and the box height is 20" which gives me 57.9" to bed rail. I have not hooked to 5th wheel with new truck. Based on my measurements I should have no problem with clearance. Am I missing something? Everyone is saying the new 1 tons are too high. I look forward to comments!