It loosens up? I have that problem some times with the standard aluminium ring - what I do to solve it is tighten it down fairly well without torquing it too much (it does have a rubber gasket at the front that one has to tighten down on) and then leave the light on a while to heat it up. After it's been on a while i unscrew the head again and recheck, but it's usually still tight. If I do this, I have no issues, if I don't and just disassemble/reassemble, the ring is pretty much always going to work itself loose.
I still haven't been able to acquire any of the actual brass hi/low switch rings though (my only experience with them is the similar device mounted in the Hound Dog and Wildcat heads) so I don't know if it would work the same.