My owner's manual has this information, at least with respect to height. Yours may too. Basically,with the bike 10 meters from the wall, with someone sitting on it, the top of the spot should by 9/10ths of the height of the center of the headlamp. They don't say anything about aiming to one side or the other. Aslo, they make sure to disclaim any responsibility for this method outside of Italy. There may be state laws about this. Anyway, the Italian standard should be close enough, I'd think.