One item on fifth wheel height - you can't be completely accurate about that until it is hooked to the truck that will be towing it.
I've seen friends measure a rig sitting on the dealer lot - then hit the AC on the top of the storage door when trying to back in. This was with a level entry for 80 feet in front of the storage building. Another friend hit the back AC on his motorhome on a 13 ft 11 inch clearance door. We finally figured out that the downslope in front of the door was tipping up the rig enough to let the AC hit.