Yeah, the V11R body has to be bored out for an 18650. The AA extenders have an even smaller ID to keep an AA from rattling. I've seen where others use 2 AA extenders, so it can be done. I'd prefer an 18650 body, but that may cost way to much to machine. An 18650 extender would be better than 2 AA extenders, and may be much more affordable than a complete body.I had the same idea about stacking the extenders but I think they'd have to be bored for 18650 (18650 wouldn't fit in the light itself w/o boring) and then a sleeve made for 14500/AA. But if you pursue this I might be interested in getting in on it because options are good!