I’m curious what others have found the smallest whistle they can play. I bought a Dixon Trad (high) E a while back and I rather like noodling around on it now and then. My fingers are just starting to touch each other. I’m curious if I could even play a high F or high G. I have pretty much a Large glove size, about 9 or 9.5.
-l2t
I’ve owned some very inexpensive high G and high F whistles. High F was no bother for the fingers, but it wasn’t a quality instrument, so I threw it out. High G was where my fingers were obstructing each other in some cases, so since it was by the same common brand as the F, and neither could produce a full second octave without the notes becoming very raspy and the intonation falling apart, they were both tossed in the garbage.
I’ve seen quite a few great sounding whistles in keys higher than D. Check Anak, Humphrey, Nick Metcalf might offer them still in the Ceol Pro or Silver Star models, Carbony.
When playing notes that high, also consider other instruments of similar design, such as the sopranino recorders and garklein. The sopranino recorder is up in a high range
where it sounds like a smooth-tone whistle and less like a nasally recorder. Plus it’s obviously fully chromatic. Yamaha makes excellent quality sopranino recorders that are
easy playing, dependable and quite inexpensive.
On his first solo record “Traditional Irish Pipe Music”, Finbar Furey played O’Rourke’s Reel on a high G whistle.
While you can hear that the whistle (most probably a Generation) is not of the best quality, his playing definitely is.
My Generation high F & high G work fine, in fact I quite like to noodle around on them, high Eb is OK, as is their high D, but I much prefer their high C or Bb for normal playing.
The little Generation F is actually a nifty little whistle. See here for example.
I used to be able for the little G but it has been decades since I had the urge to try.
The question is… would it still be “nifty” in my hands as it is in Mary Bergin’s? 
Personally the high Eb is the smallest I can play comfortably.
If that key is needed I much prefer a Low Eb.
John Sindt made me a high E whistle, some years ago. It has a wonderful, bird-like, non-harsh timbre, and is well in tune over its entire range. Our band uses it as backing for one song, written by a friend. Since the friend wrote it in EM, and sang it in EM, we have followed suit…
For me there’s the high whistles I have and the high whistles I use. This highest I have is a Susato F - I think I have only used it twice at most and then only when I needed to cut through a loud mix of instruments playing in F or Bb which is rare. I have 2 E whistles - Humphrey brass and Dixon aluminum. I have used them both on occasion because E & A are favorite keys of guitar players. I’ll bring both to rehearsal and try both but often change my mind when music goes live!!! Just whatever sounds good to my ears at the time. Again I will use these hi whistles mostly when I want to be heard over a loud live mix.
I have an Eb Humphrey also but haven’t had to use it but I have played it. Finger spacing hasn’t been a problem since I have small hands but the Humphreys are thinner than the others so they feel different.
My 2 cents on this.