If a gun doesn't shoot where you look, it's pretty hard to hit anything with it. For me, a comb that is too high makes it tough to do anything but shoot over the top of gamebirds. Surprisingly, a comb that's way too low, like the ones on many old American doubles, is easier to adapt to than you might think. You have to keep your head up all the way through the shot. I have read various explanations for why guns used to be stocked that way, including the speculation that shooting with your head upright prevented your top hat from falling off in the field.