Welcome to BLF, treehunter.
Just checking in and begging for smarter folks than me to kick in.. read the previous for details of my quandry ;)
Came across this thread, and decided to get the head off my HS-802.
I did it by cooking it over my stove with the flame directly over where the head meets the body, and turning it slowly for several minutes. Using padding on pliers (vice would work better but I don’t have), I was eventually able to separate them with minimal scratching.
The threadlock on the head of this light is crazy. It doesn’t look like much when you finally get it apart, but that is obviously deceiving.
I have a dedomed XP-G2 at 3.2A in mine. Looks pretty decent.