I just got in the Aerotank base unit made to fit the Protank 1, 2 and 3. It works really well and looks cool too. Just swap out the current Protank base for this unit and you have fully adjustable air flow. It solved the issue of tightness on my Provari totally. Here's the link:
KangerTech AeroTank Base - Sun-Vapers.com
KangerTech AeroTank Base - Sun-Vapers.com