The lower down you mount lights, the more they show the shape of the surface by throwing shadows of the bumps/dips/obstacles. The higher up, the farther you can effectively throw the beam, but the less surface highlighting you get.
For visibility by others, the more different the pattern of the lights, the more likely they are to notice you. Mount one low/left, another mid/right?
Two roads diverged in a wood, and / I took the one less traveled by, and / now where the hell am I?
'Being an adult is so much better when you forget that you're supposed to be boring' (D.Corsetto, 9/7/12)