Used to design them but pretty rusty now. I don't remember any real problems using a proper design. I did used to follow the recommendations in the old ASTE Die Design Handbook (1955) which was- under 10 inches (largest dimension across the trimmed edge) uses spring pins (requires a hole in the bolster) and over 10 inches uses the air cushion type which requires no opening in the bolster, requires less set up time and has greater die shut height than the spring type. Increased shell height does not affect the die shut height of the spring type and trimmed parts can be ejected higher in the cushion type. Quality of production is the same for either die.
They had two sample drawings-one with cam in/on the die shoe and one with the cam in/on the punch shoe.
If you designed one you probably know all this but I thought I would throw it at you just in case.
Al Kirby
askkkf@avci.net