Arggh, I don't appear to have included a link to the article where I explain what I did! Sorry! http://www.mcgee-flutes.com/Tin-whistle-retuning.htm
I think I would have just taken that from the usual maths for Just Temperament. Because I mostly play in sessions and bands with Equal Temperament instruments, I aim for best match to them. But it's an interesting thought that one should really have (at least?) two instruments - one tuned maximally sweet, the other tuned to regulation. Heh heh, there you go, whistle makers - a whole new line in marketing. "You trying to scrape by on one whistle, when you really know you need at least.....?" The whistle makers version of the shampoo maker's best sales line: "rinse and repeat".And I don't understand the "Just intonation" curve at all. To me the F# and C# should be "flat" compared to ET for a sweet tuned whistle.
OK, an interesting point I should muse over. This was my first foray into retuning whistles, and given the dismal starting point, was more of a rescue mission than Great Expectations. Interestingly, it's still my favourite whistle. But I am sneaking around behind its back....The red line looks fairly good, even though I'd prefer a flatter B, which suits me more for playing in G, and then push it sharper for playing in D.
Indeed, and I assume that this is a limitation on cylindrical whistles - that if you want to avoid low B going too sharp, you have to put up with a slightly flat high B. (But not as flat as the maker had left it - navy trace, high b at -76 cents, three quarters of the way to Bb!) Or do you reckon we can hope for better from cylindrical bores? Move the top holes down a bit and make them bigger? I don't want to fall for the trap of having oxx xxx playing a ghost Bb!And with all the tweaking, the high second octave end is still quite a bit too flat.
And can tapered-bore whistles address this issue?