Why does everybody assume that the height restriction is based on your height in barefeet? Does it say somewhere that a child must be a certain height WITHOUT their shoes on? If so, please tell me where to find that info! I would really like to know if the stick, or whatever is used to measure, is set at 54" exactly, or more than that to allow for shoes. It would seem unfair to me to set it higher, because then you might have a child who is exactly the right height, but wearing thin soled sandals, and not be able to ride, while a child who is 53.5", but wearing sneakers, is allowed on.
As far as I understand it, children are measured with their shoes ON, therefore, common sense would tell me that the thickness of the soles of the shoes would already be factored in to the measuring standards. I can't imagine any company setting their safety standards at exactly the manufactures guidelines, and risk injury because somebody's shoes were a 1/4" thicker than somebody elses.