Uncle Jaque, your tongue shouldn't be touching the whistle, even when you're tongueing. Aim it at the top of your top teeth as when saying "t", Or stop the airflow farther back in your mouth, like when saying "k". (t-k-t is the sequence most people use for triple-toungeing.)

My issue with Generations is that the f sharp on a D whistle is usually a bit flat. Presumably I should be able to address this by enlarging the second hole from the bottom, but I've never had an appropriate implement to hand to experiment. A[art from that quibble, I can't go along with your suggestion that most Generations need tweaking. I agree with Alison's oft-made point that they are remarkably good value. Occasionally poor ones do slip through, but generally they're fine, in my experience.