I’m inclined to agree with Bonnie that earlier in the day dosing would constitute better treatment or even taking hydrocortisone 2-3 times per day.

Even though Prednisone is a longer acting steroid, I’m imaging that your little fellow goes to bed at about 7-8pm.  Without being too technical, this means that the Prednisone has been in his system for 8 hours before the surge of ACTH in the morning which occurs between about 4am - 8am. This surge of ACTH (which in the ’normal’ person pushes up cortisol) instead pushes up the 17-ohp and androgens to high levels in an un/under-treated CAH person. So steroid cover is necessary early in the day to prevent/tackle this big rise. (I’m very tired so hope this is clearer than mud)!!!

There can be other implications for growth when taking a large dose at night time too. Maybe someone else can explain this in more depth.

Also I wanted to question the wording Simple Virilizing Non-classical CAH. The medical literature that I’ve always read places SVCAH as a Classical form of CAH, as SV mutations only allow for a very small amount of enzyme activity unlike non-classical which allows for substantially more.