My older Idol-Time camper was built for a long bed and I have a 6ft bed so it sits all the way back onto the down tail gate and I have not moved my tag from the bumper. The camper has been on my truck almost every day for 5 years and is my daily driver. In Oklahoma a Truck camper is "cargo" and has no tag. When I asked the state DMV I was told, the tag must be attached to the vehicle, not the cargo. I regularly travel in Oklahoma, Texas, and New Mexico, I have not had any problems over the tag SO FAR. I often tow an old truck bed trailer or a 16ft flatbed trailer for additional supplies and my son’s big go cart. The trailers have no tag on them. I have been pulled over, but only in Texas, more than once for that, but never asked about the tag under the camper. You are not required to tag a home built truck bed trailer or trailers under a certain weight in Oklahoma. I carry a letter provided free from the state confirming that is the law in Oklahoma. I know it is only a matter of time till a diligent officer stops me again. I can always spare a bit of time and am breaking no laws so after a bit I head on down the road. I of course could rant about the times I have dealt with bad officers, useless searches and the crazy hassles they caused me but 99% of my dealings with LEO have been no problems at all.