I spoke to soon on the protank. Halfway through the tank, gurgle, gurgle. Then a mouthfull of juice and juice running down my PV and hand. sigh I want a friggin glass tank that works
Issues similar to what you describe may be due to how you are vaping it... instead of just a fault of the design. Obviously this only applies in this situation I'm describing and relies on it being assembled properly with missing o-rings etc etc ...
Bottom coil designs will, for the most part, rely on a certain amount of vacuum to be in the chamber above the e-liquid. One of the common things people do that is wrong is try to vape too hard or fast with them... this forces the juice into the coil area instead of just allowing it to flow naturally. So take long slow pulls on it instead of a short quick or hard one.
An analogy to visualize what I'm talking about... Take a drinking straw, dip it down into a glass of water and seal the top with your finger. When you pull it out... the liquid remains in the straw. Now gently bob your hand up and down... nothing should still come out if you are gentle enough. If on the otherhand you use more force when you are bobbing it, some liquid is going to drip...
If you pull too quickly or hard... it pulls the juice in... each time you repeat it even more juice comes in and it starts to collect and you start getting gurgles... do this too much/often and the juice has to go somewhere at some point. If on the otherhand you do it slow and long... so that the e-juice has time to vaporize across the coils as it comes in... then there isn't enough of it left to collect.