Here’s the official word from Chris himself:
Hello Tommy,
Thank you for your message and inquiry about the flute head-joint for the
G whistle. I am in the process of designing a G Boehm-system flute and
will have head-joints to fit the G whistle sometime later this summer. I
will keep you informed of my progress.
Thanks,
Chris
There you go.
This is very exciting…I presume he is talking about an alto flute, which is an octave lower than a G whistle.
Jessie,
Is an alto flute an octave lower than the Abell low G whistle?
Yup.
I suppose he’s going up, not down–this would
explain the availability of the flute head for
the G whistle; also one wonders what the
market is like for a low G flute.
And imagine what it would cost. Best
Jazz 
The alto flute in G is a pain in the arms, but a truly beautiful sound. It’s probably the Boehm world’s equivalent of the simple-system Bb flutes, and despite the name, 'tis pithed only a semitone lower than those. I read somewhere that Herr Boehm took a fancy to the alto flute in the later part of his career. He thought it was especially good for accompanying singers.
g
What’s the lowest simple system flute that
a human being can actually play? I’m
getting faster on the Bb and wish
to sink still lower.
Maybe this?
Low G contrabass flute, a little bit more than an octave lower than a Bb!
Low G contrabass flute, a little bit more than an octave lower than a Bb!
Only elephants can hear it.
Tony
Whales, Tony, Whales.
Finally - a flute to let you play Port Na bPucai the way it was meant to be played! 