I have a class 3 receiver and use a tray type rack carrier. The carrier has a built in cable for securing the bikes, which I use, only trusting it for as long as it takes for a restroom break when traveling. I use a hitch pin lock and a bolt on stabilizer on the rack. The lock could be pretty easy to defeat but one would need a wrench or socket/ratchet to remove the stabilizer, making the rack a bit more secure. More than a few minutes away the bikes go with, or my wife or I would stay behind.
__________________
nine mile skid on a ten mile ride