Just had to stir the pot, eh?
This place is turning into “This old house”
Leaf him alone.
Aye mate,
Don’t stone me for speaking the truth! 
Cayden
But weren’t you just saying that thumbholes on a whistle are too untraditional ?
Doesn’t the C foot imply different traditions ?
I have a C foot for my SZBE D whistle (no double holes, though), and I find the pinkie reach just too uncomfortable to be of practical use.
Is that a low D ? I have small hands and can manage the hole on my Silkstone D+.
However, having lined it up against a recorder (don’t know anything about those, this one lurks in the household whistle drawer and is a Schott) the R2 -R3 - R4 stretch is about 15mm more and the holes on the whistle are larger throughout.
Double holes to match that venting might be tricky to cover though - I dug the recorder out to compare following pancelticpiper’s post above.
No, it’s a high D with a convertible extended foot. This one (click piccy):
I’d have to try it again to remind myself why I could never quite make it work for me. With the short foot it’s a rather nice “normal” whistle.
The late Paul Hayward’s web site is still up. His photo of the the Silkstone D+ :
In the description he wrote “You may find the hole a bit of a stretch if you have very small hands - it has to be fairly low down the whistle to avoid weakening the bottom D… … cannot see any drawback compared with a standard D whistle, and it is useful to have the extended range. It is also easier to perform ornamentation between the second register D and C/C#, since there is no need to go from one register to another.”
I have a couple of D+ whistles, and the 7th hole comes in handy for taps and slides on middle D and some extra finger vibrato options. And, if the low D is a bit sharp for a sustained note, as it often is, you can cover just a bit of the 7th hole to bring it down into tune.
On one of the whistles, the 7th hole is awkwardly positioned, but on the other (Guido Gonzato) it’s in just the right place. I don’t see any downside to having that 7th hole. If you don’t use it, it doesn’t hurt anything by being there, but if you do want to use it, it adds to what you can do with the whistle.
See photos of my alto below.
How does it sound, Peter?
Quite like a wood flute, but still recognisably a (loud) recorder. Possibly more distinctive than the metal soprano, which I sold largely because the standard O|XXO|OOOO C# was very flat (something that also affects the equivalent alto F# to some extent) but have regretted for many years when you’ve got viable alternatives! The low F# is also a bit underpowered with this alto keywork, in which respect I think the later version (arranged more like a Boehm flute foot) would be better.
