Pilots refused to use the A1 sight head dial to set the pipper for dive bombing. They left it at "0" which was the dial setting for gunnery and bomb aimed by experience. Rough landings and bad landings could put an eye out, bust teeth, break a nose, or put the dial into your skull. You also had a chance of wearing the long reflector plate. The A1 glide bombing sight head for the N3 is a collectors item these days. In England all P51B\C had that gunsight pulled out and replaced with a British MKII for the larger 100Mil ring at the staging depots.