That is a good idea what you are doing so far with the long tones and alternative fingerings. Make sure to keep the opening of your lips as small as possible on those high notes and keep the air stream steady. I am not good with words or descriptions, so sorry if I am not much help. You are going to have to spend a while practicing on piccolo everyday to get your embouchure ready in which I am sure you already know this.

A good suggestion if you haven't tried this already is to post this on the GFC board. There area a couple of very highly trained professional piccolists on that board that could help.

Sorry, for the limited information, but piccolo is not my specialty. I just play it and hope is sound good. lol!