There is a discussion of best altitude to be used in a ASW games forum here:
http://www.matrixgames.com/forums/pr....asp?m=2759959
and one of the participants says this:
"I asked my father, who flew ASW patrol (in the South Atlantic in 1944-45), what altitude he flew for his patrols. He stated that the "search" altitude was 1500 ft. Attacks were to be made according to the flak encountered with a "don't fire til you see the whites of their eyes" attitude to be adopted if you felt you were taking the sub by surprise. "