always towing a dink with no numbers on it. Our boat has no numbers on it either (documented) Colorado doesn't require sailboats to be registered if not used on state waters). The only proof of ownership I have ever had for a dinghy was the sales receipt. Up and down the ditch many times without a problem. Been stopped and inspected by the CG several times. Like you, our dinghies are small and used in conjunction with the mother ship. ...maybe we have just been lucky?