Just skip this post unless you want to hear a bunch of battery talk via 3rd party info...
Let's say those batteries are not true IMR, possibly a hybrid, maybe not even that. Not knowing the actual amp limits since they are not stated at slowtech, they should still be actual 2900 mah since authentic Panasonic batteries don't tend to lie about that like XXXX-fire batteries. Taken directly from comments on that battery, it
should be able to safely put out 5.8 amps (mah x 2).
Ohm's law states that you
should be safe with a fully charged battery (4.2 volts) if your coil resistance is over ~7.25 ohms. If you had an Efest, AW, or similar 18650 IMR the safe continuous amp discharge would be 10 amps, more than sufficient.
Not knowing the particular mech you are getting, I couldn't say if it will fit a fuse of any kind. Some do and many don't. I don't think I can post any links to vendors that sell the various fuses in here, they usually sell tanks and other items making them Ray's competitors.
Joe pimps a lot of stuff, almost always because it's cheap. Many lithium batteries (especially from slowtech) are only suitable for APVs with all the protection they can provide. Even with an APV, battery amp limitation is very important. If the mod's circuitry can handle 5 amps the battery needs to match that or be rated higher. Using a XXXXX-"Fire" 18350 in a Vamo with low ohms and high watts is a really bad idea. It shouldn't even work, but don't experiment with these things. I can say from experience that you can't depend on a APV's built in protection. For any mod, especially a mechanical mod, an IMR with 10 amp continuous output is a the smarter choice over unknown battery chemistry or low amp limits.
I don't think the standard disclaimers on using mechanical mods, rebuildable atomizers, and unprotected batteries can ever be stressed enough. If I was to say that using an unprotected battery and/or not using a fuse was safe, I would be encouraging the equivalent of doing wheelies on a motorcycle with no helmet or other safety gear. This puts somebody in an awkward position when answering questions like this.