I measured 9.25 inches via the Casey Burns method, so I guess I have big hands. I'm not sure hand size alone is the key thing though. For example, I think I have short little fingers relative to the rest of the fingers, so that may be why I find holding a low whistle hard. I have a Bb flute with offset holes but I think I'd have been better off with straight holes. It must have a lot to do with the overall diameter of the flute as well. The hand seems to have a pretty complex geometry.
I'm pretty sure, though, that Casey knows more about this than I do.
