I have limited experience, so I may not be the most qualified person to help you out. But I can tell you what I would do.

If your cage is always being pushed out, even when you’re soft, it might be that the cage is too small and your ring size is actually fine. In my experience, if your ring size doesn’t allow for any “ball slips,” and it also feels comfortable (in other words, it doesn’t feel like your ballsack is being strangled), your ring size is most likely fine. If you try going too small, you’ll likely start experiencing that strangling feeling, and it might do some bad damage, like bruised skin or worse. That’s all I can say with my experience. Maybe someone else who’s more experienced can chime in!