I did one of those (for a guy here) note they have very VERY poor quality optic’s (both the cheap plastic reflector’s with low quality coating and very thin and soft plastic lenses).
Also note there isnt a suitable size glass replacement, I believe they take 30x1mm, the only 30mm one’s I could find were 2mm thick and could not be made to fit.
My suggestion is to stay with the original DX21 (even with it’s lack of a tail switch), you’ll be much happier. Also be aware the 2 beam’s dont come together, they stay their own individual beam’s. Most multi-emitter / multi-reflector light (be it individual reflector’s or multiple cup’s cut in one reflector) have the beam’s join together to appear as a single beam, this light does not do that, it’s pretty annoying, like you’re holding 2 light’s in the same hand. Also shadow’s are crazy because of it.