I've found that if you take out the rubber peice that sits on the cup, then take out the little flat ring-the middle ring, then take the cap and slightly increase the hole in the middle of it, but not bigger than the cup size, you can use a little exacto knife to do this. Then when you have the hole cut out just right, you can take and push the cap down onto the cup, make sure it is in place and not pinching off the wick flow to the coil that they will not leak, and you get a pretty good th and also alot of vapor production, again when you seat the cap all the way down on the cup make sure it is just down far enough to seal over the cup and not cut off wick flow to the coil, that these things can be pretty fantastic. There is a video on you tube called cap
mod for ce2's, anyway I think thats what it is called and it works pretty darn good... outstanding actually. Dont give up becuase with alittle patience once you learn this mod you will definatly love your ce2's. I know this sounds like alot of work but it does work and make your ce2's great. I hope this helps it did for me,but I am the kind of person that likes to look at every option before just giving up.