I only know of getting the iv HC in the UK from one doctor... He set up a diabetes pump with solu-cortef and set the pattern to be more like a normal diurnal rhythm.
Prednisone is long acting and can have long term side effects. You may want to up sodium first? Unless you can get in the UK study.
I am panhypopituitary too with no adrenals. I am on dex, worse than prednisone.
Why are you looking to change your medication? Is the oral prednisone bothering you?