Just looked in the mirror, and found that the corner of my mouth is closer to the center line of my face than my eye, which is no doubt why I've never had any problem getting my eye over the arrow. Just lucky, I guess. I've always been told not to tilt my head, and never felt any need to, and now I know why. But I suppose if, because of a person's facial structure, he couldn't get the arrow under his eye any other way, maybe tilting the head would be the lesser of two evils? I know a lot of very good shooters do tilt their heads.