If you look down at the bottom of the protank, on the
threads you will see 3 holes. THAT is where the air really has to get into the
tank IF it is screwed into a 510
thread connection.
You can drill those holes open with a 1/16 in bit.
Perhaps more significantly, if you get a miniprotank, the base will fit on the protank; that means you don't depend on those three holes anymore.