I have one of these, and it is a great host. Correct me if this one is different, but mine has a screw-in heat sink and module. The solid one in the middle is the extended copper from Survival Lasers, for comparison.
I found the best way to get it all in there was to have the driver mounted to the diode and then use a blank contact board. If you have a circular driver, you could use it.
I also found that the two-cell design of RCR123's I had were too short to make contact with both the back button and the end of the heat sink module screwed all the way in. I solved this by soldering the end of a spring to my contact board to fill the distance and all was well.
Overall I think you'll enjoy it. What diode do you plan on using; do you know yet?