I've cruised the entire coast, from Port Isabel, Texas, to Annapolis Maryland, including MONTHS in Florida. I hang my anchor light from the backstay. It's a VERY bright LED unit which is no longer available, but I even on two occasions, had the FL Marine Patrol compliment me on the light.
As far as I'm concerned, at the mast head is THE WORST place to put it. I want the drunk in the dinghy at midnight, or the before daylight fisherman to see it, not think it's a star.
COLREGS states- "in the forepart of the vessel, or where it can best be seen-
Excerpt from COLREGS, rule B.30
BUT if the vessel is less than 50 meters in length it may exhibit an all-round white light where it can best be seen instead of the lights foresaid.
On the Windex- many cruising folks call that a "destination finder""

I have no use for one.