I have/had duallies so the clearance is between the TC and roof lights.
On previous Ford I had to remove roof lights covers + bulbs or they would get squashed by TC.
On new truck I have over 1" to the lights, what seems to be good for driving, but I have to be very careful with loading or leveling as small adjustment wrong way can eat the 1" very fast.
You can shim the camper higher, but that brings friction issue, bigger frontal area (fuel consumption) and stability.
Not ever talking that some TC on new Ford exceed 13' of height, so you better learn to read the signs posted on bridges.
