Actually, Blackcatter, I have seen some Brisbane Irish Players drill a hole on the back, between the top two holes, for the thumb to get that flattened 7th... :-)

Btw, I have a Generation (same length as a normal D) Tabor Pipe with the traditional two finger holes in the front and one behind for the thumb, but I find this intensely difficult to play, probably due to my minor MMD - I find that I if I just tape over the top 3 holes of a normal whistle I can easily get a Tabor Pipe that way - it's just overblows! Incidentally, I find that with some whistles, it's just as easy to play the whole second and third octaves "Tabor Pipe" fashion - keep the top 3 fingers in place and just do the overblows.

I also have the Overton "Overtone" which is a Low G length whistle with no fingerholes - played by cupping the palm of one hand around the bottom end and waggling it about - reminds me of a Theremin!!! I think this is harder to play than the "backwards whistle" mentioned above... :-)

Robin