You are most visible riding in full daylight. At night, two bright lights facing forward are better than one. I usually have one mounted on my helmet.
I use a narrow handle bar on my Mountain/City bicycle and real estate is at a premium for a couple of Fenix Bike Flashlight Mounts so I have fitted a Cinelli Euro Spinaci bar. The Fenix Flashlight Mounts work well.
The Flashlight mounts fit either side of the Spinaci clamps on the Bar. They also give an additional tribar aerodynamic position on the bicycle.
This allows me to fit a couple of Hi-Low-Flash mode Cree XM-L T6 18650 600-900 Lumen flashlights without the flashlights getting in the way.