A lot of the complaints are around the placement and size of the air flow holes, too. But, seeing as how the heads are THE most important part of the ProTank, and if the quality of them has gone in the toilet, holding off from recommending them is probably a good idea, if and until the quality resumes, or the buyer is willing to rebuild them to work right, or drill the body to improve airflow.
Also, you're in the same boat I might be in - our gear is older - most of the complaints are regarding newly bought gear. It could also be that clones are being sold as authentic Kangers - which is another reason to warn people if they buy them.
I absolutely love my Pro Tank 2 and P/T mini..now
When I first got them it was like sucking a golf ball through a 50' garden hose to get a hit. The three vent holes are only 1/64. I opened them to 1/16 (to just barely touch the threads) now its like breathing in air with tons of flavor and vapor...also I dont get that burnt taste any more while vaping no matter how much I toke on it.
As far as the coils go, my local B&M shop taught me how to rebuild them and a little trick to help,
use #32 wire to make the coil, use a #4 finishing nail to wrap your wire around, put the first wick under the coil rather than through the coil as they come from the manufacturer, place the second wick on top of the coil (just like out the package). Where the opening is inside the glass where the juice flows onto the wick put a small piece of wick in there...1 side (see picks)

