I Was able to put inside cartgidges with caps!!!Eroll pcc mega-how to put inside tanks with caps...hard,but it could;-) - YouTube
Its getting them out that's the fun part.
I really can't understand what joyetech are doing with this, 3 extra tanks aren't enough to use up the PCC charge, so you are going to carry some more anyway, and then you need talons of steel to get them out, or put up with a lot of leaking.
Do the eRoll-c carts have better seals so that they wont leak without caps:
I wish Joyetech would just do a classy little box with a 3 x 3 grid of spaces for capped tanks, that you could insert either way, so you could keep track of which were full. A bit like the tin on my avatar but done by someone skilled and a bit bigger.
Having done all that whinging, the extra charge and the 3 charging slots work really well.