This is the way I understand it: Out of Ground Effect requirement is because the airflow is more streamlined over the wings, and therefore more airflow over the rudder, when the airplane is in ground effect. When it leaves ground effect, the wash over the wing has more of a downward deflection, reducing flow over the rudder, decreasing it's effectiveness. So if manufacturers could certify their aircraft with 30degrees bank, and in ground effect, the speed would probably be 30KIAS! haha