Out of curiosity, what's the difference between a hockey head form and a football one? I don't think hockey and football players have structurally different skulls, so as long as the study accounts for the fact that different helmets fit different shaped heads (which I assuming is also true of football helmets since I haven't worn one since getting a concussion was called getting your bell rung and you could go back into play as soon as you could see straight) and using head forms that match fit, what difference should it make if it's a "hockey" head form or a "football" one?