Well, I guess I was a little overly optimistic in my choice of keys for the instrument. “G” is going to be ok, but “F#” and “low D” definitely won’t work for me. The finger stretch is too much & pipers grip just feels awkward. 
I think I’ll try going the other direction. (“G”, “G#”, “A”, and “Bb”)
Early prototypes will be made out of pvc pipe (modern bamboo) with actual bamboo instruments to follow later. My first prototype “G-1” is rather crude but it doesn’t sound half bad for someone that has never played a reed instrument before. 
I’ll post pictures and sound files after I’ve done a little more fine tuning.
Sorry for the non-whistle related post. An update was requested in another thread and I couldn’t find an appropriate section for this type of reed instrument. 
Fractalfingers