Remember, disappointment is to be expected when trying to “lego” parts — all you can do is report your own observations, but we know from experience that Chinese lights don’t have reliably consistent threading.
Hmm… Any chance a DQG Hobi or Fairy tube would lego with those? If so, there is a short extension tube available for those from Banggood. It should be long enough to fit two button cells back-to-back with a divider in the middle, to light up both lights. There are actually two versions of the tube, one with a divider already and one that is just an open tube. I have both.
The Convoy S2 vs Convoy S2+ 18650 & 18350 tubes!
As posted on another thread, the Convoy S2 gray (bought from Simon) can be used with the black & desert tan 18650 tubes and the gray, black & desert tan 18350 tubes!
Also, the S2 gray tube can be used in the “short” Convoy S2+ (blueish gray) [no photo of that one, sorry].
The Skilhunt DS20 legoes with the (shorty) battery tube of the BLF-A6. The o-rings do not engage at all so the combination is not waterproof, but it works fine on a 18350.
The Nitecore P12 tailcap fits perfectly onto the Nitecore P30. It makes it easier to use a lanyard without having to use the tactical ring on the P30, and it will tail stand. Tail standing is not perfect because the rubber boot on the P12 switch is a bit taller then the cap. However, It does work as you can see in the pic.