I thought I'd check these out after reading this thread, and picked up some at Costco.
I was able to remove the head as Simon520 suggested.
Also, I was able to loosen the headsink too. How I did this was using an adjustable strap wrench, and with the head still removed, I turned the lower adjustable zoom part of the head, as if to tighten, But Without the rest of the head back on, this seemed to loosen the heatsink. Not sure I clear on saying what I did, so stated another way, I just did the opposite of what I did to loosen the head, BUT without putting the head back on. The heaksink should be loosened. I wanted to play around and upgrade, having just learned to upgrade 4 old flashlights with SSC P4 U-bin, so was trying to find out loosen the heatsink, since I had a bunch of extra circuit boards from DX.
So hope this helps someone.