When I had my T/C always moved the tag to the camper. As it was 36" under the camper if left on the truck. When we picked the camper up in CO, I did not move the tag. Tell the truth I was so happy to have our new T/C I did not even think about it. Headed south to NM to my in-laws then home across I40. Had one trooper in TX ask about the new camper. And told me I need to move it to the camper. As he could not see the tag. But the guy was nice and followed us into the fuel stop. And even looked under there at the tag.
After that I always moved it. Only one time did I forget to put it back on the truck. Tn Trooper pulled me over and told me my Tag was still on the camper LOL He lived down the road from me.
Pete