What time do you give the morning dose?  My son had the same problem and we started giving his morning dose at 4:30am.  We were able to cut his cortef dose almost in half!  He was taking 37 1/2 mg and was still off the charts.  they reduced his dosage to 20mg and the results were amazing.  We still dose after school and at bedtime.  It might be worth a shot just to try this minor change.