Chiff and Fipple Forums

Evening all, I just purchased an Aulos Stanesby flute, and I'm having difficulty fingering the f natural and f sharp to make the difference in pitch noticeable, whichever fingering I use, there is minimal difference between the two notes. I have played all sorts of flutes including a Folkers and Powell Denner copy so I have some experience with forked fingering. Solutions anyone? Thanks.