Vapor production also goes hand in hand with air flow, and there is not much you can do to get more air flow without an airflow controller or modifying you Zmax's air flow channels, or the base of the protank and center pin of the head on a Protank2. Another thing, why oh why do people use 28ga or larger wire in a Kanger style head when using a regulated device, that is a another factor of your vapor production, 28ga at that many wraps takes to dang long to heat up, thus why you are having to crank it up to 11.5watts. Step the wire thickness down to 30ga maximum, plus you also have to remember, look at what device Rip Trippers usually has his atomizing devices attached to, a Phazed DNA20, also have to remember he has most his atomizer attachements modified for maximum output for high power output and doing lung hits most times during his demonstrations. Wanting to fog up a room with a Protank design, find a Protank1 someone doesn't want anymore, its airflow is far better than the Protank2 which is more restricted, and it can be done because I have done it, but only with a Protank1 using a 0.7ohm nano-coil head with a cotton wick on a SmokTech Natural and SmokTech Magneto, both mechanicals, using MNKE 18650s with a resetable fuse on the battery, but still I am not getting anywhere near the clouds Rip Trippers is doing.
A properly built 30ga micro or nano coil in a protank, should by my experience produce triple the flavor of a stock head, twice the throat hit, and twice the vapor of a stock head in an Evod, T3, UniTank, or Protank2, Davide, or other such device using a Kanger style BCC head, Protank1 and possibly a Tatroe or Davide tank might reach the Protank1 with four times the flavor, twice the throat hit, and triple the vapor, but as I said above to achieve that you are needing a sub-ohm micro or nano coil on a Mechanical, going that route, cloud chasing, better start doing your research into RDAs, battery chemistry and safety, ohms law, and sub-ohm safety, you'll not get massive vapor out of a Glassomizer/Clearomizer class bottom tank system, they are not really designed to be fog machines.