I just wanted to say thanks to Jerry for the excellent tweaked Generation he just sent me. Here it is pictured with my self-tweaked Generation. There really isn't any comparison.
The best way I can describe it is it is much "smoother" to play. The transitions between notes feel seamless on this whistle. I can't put it any clearer than that.
And much to my relief it looks very much like my earlier problems with Generations were to do with the whistle and not with me - because this excellent whistle doesn't pose any of the problems I had earlier encountered.