Angie - If you have no luck with shimming, contact Spellbinders. Go to their site and the number is there. Don't bother with the store where you bought the die. Spellbinders will replace a defective die.
Cakhuxel - I'm starting to practice with my Prismas and I think I am improving a little. I got the softer stumps from Taiwan, and I also found that plain mineral oil seems to be better than baby oil. Go figure. Baby oil is merely mineral oil and fragrance. But to me there seems to be a difference. And it's nice not to have to deal with the fragrance when I'm bent over something, coloring.