Do you crochet all the stitches all the way around--make a circle using the stitches that were on top of and on the bottom of the contrast yarn? I'll check my EZ books and see if I can find anything on this.
You could also try sending an email to www.schoolhousepress.com
and ask them. I don't know if they answer this type of question, but it is run by EZ's daughter Meg Swansen, and my dealings with them have been very positive.