I just attended a CAH Symposium on Sunday at Princess Margaret Hospital and the endocrinologist who spoke first was our own endo.  One of the questions asked was to do with Prednisolone and growth and he stated that this particular drug is often associated with poor growth in CAH kids.  He said that kids were usually better off on Hydrocortisone until they were through puberty and if they did need a bit extra at night then sometimes he prescribes a prednisolone dose at night. I would look into getting off the prednisolone altogether if you have growth issues and try the Hydrocortisone.