Since you made all your forming gear from scratch, a ring with a slightly conical hole and a bushing with 4 slits should be easy.
Given that the near cam point of the RCII should be enough in a step or two. Personally i would use a 4ton hydraulic press.
But if what you have works fine then let this be a thought experiment.
What im thinking of is something like this:
http://www.larrywillis.com/