Thanks, Jerry. Not knowing much about ITM or whistles (and even less about Theravada), I wasn’t sure that most of my posts weren’t just irritating.
As to the repositioning of the Feadog (or any whistle of that type) head …
The hot water worked quickly. With the mouthpiece off, I was able to get a better look inside it, and I didn’t see any obvious irregularities.
Moving the mouthpiece about 1/8" out already helps a lot, but I’ll try the tweaking as soon as I get a chance to look for the blue tack. I’m pretty sure I’ve seen something similar at Office Depot.
I also decided that the Clarke was taking too much air, so I did as someone here suggested, and flattened the arch a bit (after using a bit of tape over the top of windway opening to test the effect). Sure enough, it did reduce the air requirement a bit. It’s much easier to play now. It may be a tiny bit quieter now, but that’s okay with me. The sound of the Clarke is very plain, compared to the Feadog and the Dixon, but it sounds good with diaphragm vibrato, which is easier now that I’ve modified it.
It’s also much more even across the first two octaves, and I’m less likely to jump an octave when I start getting carried away.
So far, I have the most trouble with octave jumping on the Dixon, and it’s generally the most sensitive of the three to the amount of air pressure I put out. Sometimes it seems like each note requires a different amount of air to get it just right. I assume that this is something that will become second nature with enough practice, so maybe I should play the Dixon the most at first.