Now you have my curiosity piqued! I have played with some (amateur) groups using my soprano and sopranino recorders as whistles. (By the way, Barbara, well made recorders are usually quite well in tune. The sopranino will loosen your fillings; but) I don't know if they have the power to remove them.)

Are they chromatic or diatonic? Do tin whistles come in pitches, or do the letters "G" and "C" that you refer to describe some other attribute.

If they are diatonic, what scale do they sound. From the phrase "six hole", I suppose they have an incomplete scale or use cross fingering to get the extra notes.

Murray