Well - that "whistle register" is such a stupid debate - I tried to find out a bit, but it seems everyone has different definitions. I was told if I can go with a "male" voice box to above 700 or 800 Hz, it has to be whistle register already. So I dont know really. I know my screams are probably getting in the 900 Hz range and that is pretty squeaky - I have no idea what to expect post VFS. if it stays, it is ok, my upper limit seems to be unusual for a testosterone damaged voice box, if it goes up, i will be thrilled, I hope it will not go down.