In 1965 the American Richard Schreder flew a variant of his HP-11, which in normal form had simple flaps as airbrakes. To comply with the rules, the ship was modified for the World Championships so that the outer half of the flaps hinged upwards to comply with the rules. Schreder pointed out that this made the glider more expensive and less safe (higher landing speed, less effective brakes). The argument over whether to allow this went on for the next five years in IGC and eventually the rules were changed to permit plain flaps provided they were the only means of drag control for landing, and there was no aileron linking for camber changing. There were no other limits on using the flaps for lift increase (although the lack of aileron linking meant that the flaps were not as effective as they might have been).