I skipped my remarks on Shaw whistles ... I was going to say that Dave Shaw seems to think that all whistlers have the lung capacity of pipers!
I still don't really know how my Shaws sound ... by the time I get a reasonably coherent phrase out - hyperventilation has set in and I'm getting high on oxygen.
I have heard of "tweakers" reworking Shaw whistles ... mainly by cementing in a thin strip of plastic (~) to narrow down the windway. They are made of material much too sturdy to "nudge" in and out the way I always did with the Clarke tin whistles.