Playing with lift. Talking to a delta wing fighter driver who had a penchant for low flying related how if you had the aircraft sitting on the ground cushion you could push the stick forward and the nose would lower, but that's all that happened. Amount/degree of 'push' not elaborated upon. The only explanation I could come up with later when giving it some thought was the increased camber by the elevons being deflected down counter balanced the "loss" of lift due to the reduced angle of attack, so the status quo remained. Not a chap inclined to stretch things for a good story.