I have the small DCT and blew a gasket on the inside of the cap. I used an o ring from a kit you can get at the hardware store , it wasn't a perfect fit but works fine: it's a wee bit small but stays in place. I nicked the orig when filling and sliding the carto back up; that SS carto edge is sharp (rookie move). Now I slide the cart just into the cap, insert a rubber ce2 tip
CE2 Tip Single to protect the ring, fully push the carto in and switch to my drip tip,
I don't slot my carts, just that stock tiny hole and only occasionally have to slow down my chain vaping when using my EVO on middle setting (SR carto)to let the juice wick.
My friend bought a gas station 0 nic ecig that came in a tube with rubber plug ends. five minutes with a hacksaw and pipe cutter and I have a free DCT! The end plugs are about 1/4 inch thick, I just used a dead cart, hit it with a hammer to cut through the plugs and it seals perfectly. Of course its ten bucks for one of those ecigs so unless you have a friend, just buy a DCT!!
Not sure what the point of that story was.