.308... i've modded a CNC 123 to fit a 20IMS.. the bezel of course did not screw on completely, but i think that the upcoming groovy bezel is a perfect match for that particular mod.. i.e. putting the 'groovy' bezel on a CNC123 will give the extra length to fit an IMS20..
To get it to fit you need to shave all the legs off the reflector and do a little bit of grinding inside near the 'goesout'.. i just used a dremel.. the original bezel will do the trick but you see the threads, so at least you could have something that works 'til you could work out a deal with photonfanatic to get a bezel from a groovy.
You could see if there are any LionCubs left :-D.. that comes with an IMS 20 : (i'm kidding).
seriously .. if you have CNC123s and IMS20s.. try making one fit.. send a PM to photonfanatic and see if he'd be able to make a groovy bezel available to you.. maybe an over-run or something once they production is done on those lights.
-awr