We had to bribe our DD, she was nine at the time, to ride RnR...it took thirty bucks and the Disney Barbie but that's another story for another time. Anywho she was just at four feet at the time and the shoulder harness swallowed her! I kept looking back to where my DW and DD were sitting and all my nine year old was doing was scowling...yeah it wasn't amusing to her but we found it rahter funny to see her head lost in there. She got rattled around a bit during the ride as well which wasn't amusing at all. So I think even 48" may be something of a stretch if you don't want to have to worry about Aerosmith laden head trauma.