I think that it’d definitely be possible in a smaller AA light. There’s room both in terms of length (I had to use almost the full length of the 1/2” HD copper coupler in order to get the emitter board+Carclo optic pushed up far enough to the lens. I think I had to cut off only maybe 1/4” of length.
Width-wise, the head diameter is also maybe about 1/8” too wide on each side (or total 1/4” too wide), compared to the Carclo optic, which is ~24mm, I think.
Finally, the neck of the head part is a bit wider diameter-wise than the outer diameter of the 1/2” copper coupler, so the coupler (which is kind of “the pill”) is not making great contact with the head or body. I probably could do an aluminum foil wrap like with the P60 drop-ins to improve that, but this whole exercise was more of a “can I do something neat with this junk light?” exercise.
Note that even though the pill contact with the head/body isn’t that great, there isn’t a problem with the negative side contact. I think that this is because this light is designed such that the path for negative is via the front edge of the mechanical side switch to the negative/ground ring on the battery side of the pill.
I followed ImA4Wheelr’s approach ("Police Light" Version 2 - 14500, Nanjg 105C, & XP-G2 Q2 7C4), and used a copper coupler from Home Depot that I cut down as the “pill”, and then soldered the driver to one end and attached the quad emitter board to the other end.
. . . I probably could do an aluminum foil wrap like with the P60 drop-ins to improve that, but this whole exercise was more of a “can I do something neat with this junk light?” exercise. . .
Well put. You just articulated what motivated me to do those "Police" lights. You were forced to basically custom build the guts of the light from materials meant for other purposes. In my case, the "exercise" helped build on skills and changed the way I look at at a light when I want to mod. Currently, I have about half a dozen lights that I am replacing the normal pills with custom made copper pills. The copper is from plumbing and roof flashing materials. I have had to learn how to make my own custom sized tubes. These are "big boy" lights that will running at high currents, but it was the cheap light exercise that has opened this option to me.
Copper and aluminum flashing is great for situations were you have a gap to fill. It is strong enough that you can create a "tube" with it and lightly press it into place. I can't find copper flashing around here. So I use aluminum. Keeping just one of these will around is really good idea for a modder. You can flatten it out for storage: