Do they actually require an inch of height more to account for shoes? We are 4 months out and barefoot DS is measuring 38 3/4s. He will probably grow between now and then and might just be 40 inches. I, obviously, don't want to push the issues as I know the restrictions are there for a reason. I just was wondering if the new racers in Radiator Springs might be feasible if it is a 40 inch height restriction.