I might be too late here, but hopefully not. I use a small rubber strap wrench (the strap is about 5/8" wide) with the light placed in a vise. My vise has rubber jaw inserts, but you can line the vise with tape or cloth to protect the light. Back the head out counter-clockwise by hand until it stops, then use the strap wrench. Once the head is removed, place the strap wrench on the remaining top part of the light (the part that moves to focus the light) and tighten it clockwise. This part gets locked in the full-out position when removing the head, so you need to "pop" it loose the other way.
I've removed the heads from 80+ of these lights. About 5 of them came loose by hand, 4 or 5 were REALLY difficult even with the strap wrench, and the remaining ones came loose without too much trouble by using the strap wrench. The bigger strap wrenches (one inch wide and up) just don't seem to work as well as the small ones. :shrug: