For those interested in using Home Depot's 51 LED Defiant flashlight as a host (while they last) there are several points to be considered. I so enjoyed my first defiant build that I went out and bought three more to use as hosts. Even at full price of 10 bucks these are a great deal considering you get the host, 4 alkaline AAs, and the battery holder which can be modded for high current. There are two distinct variations of this light which unfortunately can't be determined in the packaged state.
The first comes with a white internal switch housing and accepts a two inch diameter aluminum rod like it was made just for that purpose. This means no diameter filing of heatsink or host for those wanting to make a stubby tripple or quad. Unfortunately this version does not accept 4 eneloops without damaging the skin of the battery on insertion.
The other version has a black switch housing and will not accept the two inch aluminum rod. Because of the compact nature of this host tolerances on a single emitter build will be tight and will require a thinish heatsink even with a shallow reflector. The plus to this version is that the body is bored slightly larger and will accept 4 eneloops without damaging the batteries. Bezels and tailcaps are interchangable between variations but not tubes and heads.
The switch housing is not viewable by unscrewing the head but is viewable from the tailcap end of the tube after removing the tailcap and battery holder. There were no obvious differenced in the packaging.
I was hoping to open up the ID of one of the narrower battery tubes to more dependably accept 4 eneloops. I wrapped a large drill bit with sandpaper, chucked it in a drill press, and went to sanding. I did open the ID by about 0.012" which was a fine fit but found the cheapo threads were a sticking point. I lightly sanded the threads and...oops. Now the cap goes on but only has about 3/4 turn of threading left. And I have skinned eneloops from the test fitting. I also wrecked a micro mag build and burnt my elbow on the soldering iron that day...others may have better luck.
Thanks for the report KYfishguy. The tube does seem to be the biggest challenge in this light. It seems the worse point is where the threads just end. I think smooth that point may be adequate. I hope.