As to your question about being over and undersuppressed at the same time, I believe personally a child can be and infact often is because the dosing can never be perfect at any one given time for anyone child.  For example a child may be dosed twice daily as opposed to three times daily and get a large whacking dose of hydrocortisone 2 times a day at say 8am and 8pm.  This type ofdose at 8pm is very growth restrictive and infact over suppresses the adrenals and other vital hormones required for growth, tissue repair etc.  At the same time such an AM dose is practically non existent by 5pm which means your child is undersuppressed at that time of day and goodness knows what the blood test would be showing really if taken at 5pm - perhaps you should have a 24 hour profile done of your daughters dosing regimen to examine that and ask your daughters consultant about that stating that your not happy with the current symptoms and think she is worth it.  It doesn’t bear thinking about really if thats not done. Not too mention the fact that there are rather rapid blood sugar alterations that can verge on the diabetic basically with such a dosing regimen as above! 

Even three times a day dosing can be lacking for a child at a certain age and for fast metabolisers etc.  This is when you also need to look at the type of replacement your using really not so much the timing of it.