The madvapes tank you are describing is not the one pictured in the first post on this thread? If so that is very much the smoktech one, I use the exact same tank as I mentioned previously but the smaller 3.5mL variant and I fill it as you described by pulling down on the carto to expose the hole in the top. Is it that it does not pull out the bottom at all or its very tight? I hate for you to have to toss out a good tank.