big flute

Michael,

"Wait, I don't see what you mean. If the holes had circular top views and
were the same width as the bore, they'd come down halfway on both sides,
like a saddle."

exactly, their not really holes anymore, they're slices out of the side of
the flute. That's the limiting case where the shortened air column acts as
if it were a tube without holes. But, as you said, you can't work the
holes with you're fingers anymore and you'd need some kind of key mechanism
(but with a flute long enough to get higher harmonics you can't reach the
holes anyway, unless it's a piccollo range.) I've been playing with the
idea of a flute like this designed to play harmonics 4 - 8 on each hole,
and it works beautifully except that my mechanical abilities stop where the
key mechanism comes in. Anyway, this is probably getting remote from your
own project . . .