I'd suggest a light application of jellied fuel to the entire body of the whistle - this allows not only for solving the drip problem, but then also allows for a spectacular solo number on flaming tin whistle.

But seriously...

I know what you mean, Melani... I also have had the wonderful 'occurence' where I could actually hear some of my whistles drift in and out of tune depending on the heat. I've heard that brass whistles are REALLY bad on that - the two people I most trust on the issue have 'studio' expensive brass whistles that never see the outside of a building, and also a set of 'play' whistles for use in less controllable situations.

M