Short wicks work well because the liquid can get to the coil easily, particularly if the wicks are unraveled. Old fashioned factory made atomizers always had short wicks, if you dripped a couple drops it was absorbed by the wick and coil instantly.
In my vivi I have trimmed the wicks to just a bit wider that the tank, when I tilt my PV to take a draw the liquid floods the wick, draws into the coil. (never could figure why vapers would want to walk around staring at the ground to vape...

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The Vivi is an improved version of the old CE-2 with a MAP (MostAngryPirate) tank. The CE-2 worked well if the wicks were trimmed and fluffed up. Both the CE-2 and Vivi work better using lower wattage, they don't need the max-power of other toppers.
The BCC are an offshoot of the old Kanger bottom coil cartos, (like the Smokless Image cartos) with the filler removed, a tank added and the wicks to hold back the juice from flooding the coil.
The bottom line for any atty, carto, tank, RBA, etc. is for JUST enough juice getting to the coil, turned into vaor, and being replaced at a steady rate so the coil doesn't overheat. Many different systems have been tried but we are still in search of the Holy Grail of Vaping Toppers...


Most of the equipment today does an acceptable job, yet dripping or bottom feeding, both a manual application of the juice is still the best fine control.