Originally Posted by
Richard Cranium
If you want the light to work at its best - then you mount it directly in your line of sight. (high up)
If you want to be cool and not bother other riders around you - you mount it low, like on the fork or skewer.
Keep in mind that if you mount your light really low, like on the skewer - it is more likely you will need help reading some street signs.
By mounting your lights lower the beam casts a longer shadow ahead of obstacles... this greatly improves response time as we see the shadow before we see the object.