I would guess 48" is pretty good guess. I do know that they are not consistent with it. So if one doesn't let you go, you can always check when a different person is running it. I saw many little ones going. I know that on a roller coaster you would never want to do that on a roller coaster where safety is an issue but in this case there is a net below that it doesn't matter how tall you are, it will catch you. I think this has more to do with being able to reach the peddles.
Good luck!