My previous trailer was about 4-5 inches. There were some times when my 5th to bed-rail clearances became very close on uneven surfaces. On just once occassion, the trailer did touch the bed-rails, and left a very small tweak. And I mean small, more like what hail damage (a single piece of hail) might look like on the rail. So something to think about.
I could have raised the hitch to gain more clearance, but decided I wanted a level trailer and told myself to be careful.
My current truck/trailer setup has much more clearance.
