The chimney tube has a larger ridge above it's o-ring so it can only go in the chamber's cap till it bottoms. If the
tank doesn't screw on far enough to seal on the o-ring the threaded end (top) needs to be machined down ( sanded in my case) till it get to desired spot. After that the upper AC ring will have to be reduced next till it fits, I try to make it so the
tank locks the ac ring.
Here are some pictures, maybe I can add to this when I get home.
The o-ring that seal the tank bottom:
Tank not sealing on o-ring:
Tank in desired spot (could be farther):
If it doesn't screw on far enough this piece needs reduced on top side:
Next, check how much needs to come off the side of AC ring without the knurling:
Lastly, my machine shop:
And I know I'm still going to order the 22mm EVENTUALLY, but I wanted to give the other 2 tanks I bought recently a chance - which are the Crown and the Aromamizer... Both have proven themselves to me - I like both of them for different reasons. I feel the flavor is better from the Crown and their pre-made coils, but the Aromamizer is easy to rebuild and the airflow is insane. 
