Because usually if I don't cross them they chafe at the fuselage sides. Crossing them (For me) seems to work better and gives them a straighter shot to the control horns. I'm pretty sure that in the case of a Midwest Super Stearman that this will work as a benefit. As far as a reference as to where I heard or read about this I cannot remember-I wish I could. I do however encourage you to do your homework and research this if you haven't already