Mounting the lights low makes them more effective because the vertical separation between the lights and your eyes brings emphasizes the texture of the road and makes it easier to spot debris and potholes. This mounting is very popular among randonneurs who ride many hours at night.

The location will cause shadows from the tire that go off to each side, but using two lights will fill those shadows. Even so, it's a minor annoyance that you quickly get used to.

Just be sure that your mounting to the fork is secure.