I use the smaller tanks with a full sized DC carto. First, it gives me something to hold
onto when screwing tank onto mod ( the extra bit of carto sticking out the top of tank ).
Second, I bought a bag of o-rings from Home Depot ( #6 I think ), and slide one
down over the end of carto so that it is tight against the top of the tank.
This keeps the tank from sliding upwards.
For extra capacity in a short tank, I prefer the Phat tank from elsewhere.
