I have a super skimmer 65 on my small tank. I've never had the overflowing cup problem, but in trying to rid myself of the microbubbles that mine creates I did have it jump up quite a few times. From reading about them and from a little bit of experience, I'm guessing that you are somehow restricting the output and increasing the pressure inside the skimmer. This includes putting the output too far down into the tank, running the output from the skimmer any way but sloping downward, or jamming it into the bubble trap so that it creates back pressure. If these couldn't possibly be the problem then I don't have a clue. Good luck.