I bought two 3.7 volt ultra fire batts when I first started out last month they are 15270's protected. They are 28.9 mm each.
the only ones I own. The mod you saw is 71mm inside battery comptmnt. my 18650 is 68.2mm I need to post which batts work perfect inside the mod. I didnt figure is was a big deal. You proved me wrong. That is how I had observed others "doing it" on videos about the journeyman and someone even used foil.
Generally if a mod will take an 18650, it will also take the Tenergys and AW 16340s, a better choice than the 15270s and with no magnets needed. You will also find out that the 17670s will also fit-I'm not worried about the batts.