While I sympathize with you, my concern would be is the safety mechanism going to hold your son in securely enough for him to stay on the ride. In several instances I can think of the harness or bar might not fit him properly if he isn't the right height and he could be injured. I know he will be disappointed, but he'll also be unharmed. You have to decide if it's worth it for you. I know my SIL used methods like this on our last trip and sometimes she got away with it and sometimes not. My niece was very upset and crying on a couple of occasions, but she soon got over it and moved onto the next thing.