I generally vape at 50/50 or higher in the VG department. I've never really had a leak that I can think of and I've had my -C for a month now. Some things that the vendor showed me when I bought it ... when putting an atty in, drop it into the cone and let it settle in it's proper alignment, then screw on the base. I know all the videos for the -C show putting the atty on the base then screwing the cone on, but I can see where one could get it a bit out of alignment that way. Keep the tank vertical with the mouth piece down when you put it into the cone. Push hard until it is always the way flush. The newer the tank, the more resounding the click will seem. Slow steady drags seem to be the word of the wise as well, so you're not pulling more fluid in than the atty can handle. All I see when I pull the tank out is condensation, and there's going to be no getting around that. All in all, I personally like the tank system of the -C. I have a DCT sitting at my vape station that I never use. Well, part of that is that it has a dual coil carto in it, and the eGos don't really put out enough power for it, even on the Twist I find. Once I get some single coil cartos around 2.0ohm, I might try the bigger tank again for sitting around the apt. But for on the go, and the way I like to change flavors a few times a day, the easy of the A/B (I have smaller A, think the B is too bulky personally) can't be beat. I did finally buy a drip tip tho for my 2nd cone so I can really change up the flavors now through out the day if I so desired.
