I have a davide and THREE protank 2's. One protank I bought off a buddy and it worked great. Awesome airy draw just like the davide. Liked it so much I bought 2 more. Well they had such a hard draw I thought my eyes were gonna pop out! Plus one wouldn't even pull at all! OCD as I am with making stuff work I drilled the three holes out to 1/16" AND added 3 more. Also ordered a airflow controller since the V2 threads are crap the controller helps "save" the v2 threads from excessive tank changes. And now the tank that wouldn't pull at all pulls and works with the controller installed (weird).
So with all installed I still get a better draw but still too tight for my liking. I found out when the tank is tighten all the way down it's actually smushing the bottom seal and fairing it out blocking off all air flow! Easy fix! Back it off. And screwed the airflow controller slam up against bottom of the tank and presto!!! No loose tank and a AWESOME DRAW!!!
Granted the davide tank was perfect out of the box, I didn't like the amount of liquid I was loosing on the stem of the atty when I went to refill the tank. Let alone if not whipped of, the juice that was being shoved in the center tube. For some reason the protank 2 keeps the stem darn near bone dry when removing the base. Just my opinion and help

if needed
HAPPY VAPING!