350watts is unattainable unless you are on some type of 4s LiPo battery mod, with 18650 mods it is a red herring, can't be done in most cases.
Triple Battery Series mod
350watts/9.6v lowest charge/90% Mod Chipset efficiency=40.5093amps needed (3.2v per battery lowest charge X 3 Batteries)
Quad Battery Parallel Series (these are bit newer, 2 series sleds in parallel, gain about 50% more CDR than a single battery where a straight series you are limited to CDR of a single battery)
350watts/6.4v lowest charge/90% Chipset Efficiency=60.7639 amps needed (it is a bit of a confusing configuration of batteries, lowest voltage of a single dual battery series mod so 3.2v lowest X 2 batteries, even with LG HB2, 4, or 6 batteries which are true 30amp CDR batteries, the highest CDR of any 18650 on the market, 30amps CDR +50%=45amps CDR the mod can maintain, 16amps over at about 61amps)
Quad Battery Series (even if they make one presently)
350watts/12.6v/90%=27.7778amps needed (3.2v X 4 batteries) <--- LG HB2, 4, 6 only batteries that can handle this load.
350watts is just unnecessary, it is the old game of who can piss the furthest to the urinal, just my opinion. If you are needing 350 watts to push your coils to operate properly, you seriously need to rethink your combination. Airflow, type of atomizer/tank you are using, types of coils inside the atomizer. This game of mine is bigger than yours in vaping is getting tiring, just like Efest, Imren, Eizfan and other battery re-wrap companies rating B and C bin discard batteries at higher what A bin manufacturers rate the A bins as are way overspecced (hint the LG HB2, 4, and 6 are the highest CDR batteries on the market presently, any battery that says it is 35amp plus is a re-wrapped battery, buyer beware, LG, Samsung, Sony, Panasonic/Sanyo are the big 4 battery manufacturers everyone else buys from in most cases).
O/T
With any tank, even with an RBA, the key principle is prime the coil properly, crank the watts down lower, generally 50% the lowest rating, then gradually break in the wicking and up the wattage in stages every 15 to 20minutes constant use, until you get to your happy place, if you get even a hint at a harsh hit back it down a notch, that is the max that coil handle even if rated for higher, moment you get a burnt hit, coil (actually the wicking of the coil which is the weakest part) is toasted and ruined.
Just because Jonny "I Wanna Be Looking" Kewl is doing one thing, doesn't mean you yourself need to follow, for you never know if Jonny is blindly running toward the edge of a cliff to fall, with high output vaping, that cliff edge is the decider of a battery staying stable and continuing to work, or the bad ending, the batteries vent or explode due to the abuse, which is a rapid visit to ER with shrapnel wounds and major burns, don't be the next vaping accident just came into CNN's news room, you are ultimately the only one responsible for your own safety.