With a weaver stance, I think I tilt my head a little (I shoot Expert level). Basically, don't think about it, do what works for you. For every shooting coach or writer that tells you you have to stand one way, there will be another shooter that does it "wrong" and can outshoot him every time.
Dry firing and mentally calling your shots are the second best thing you can do to improve your shooting, after live fire. Maybe before live fire, really.