Yeah, I immersed the fipple in dishsoapy water and it solved the problem. I love the sound of my two-whistle set (C# and B). To my knowledge there’s no sound out there like it. And it 's odd–I can’t figure out why, but the B is easier to reach than my two C whistles (I have small hands). It shouldn’t be easier, but it is–somehow. These are nice whistles for the price.
Used to get clogged before a tune was done playing, but now I can play for a good long while.
Yup!
I’ve never heard of this dupanol stuff but, Surf laundry detergant seemed to do the trick for my C clogging Syn! So, good deal. I’m happy. Now I still need to get around to tightening the brass tuning barrel on the fipple end, and I’ll be set. Cool deal.
As for wooden fippled whistles, such as my original clarkes, they NEVER clog. And I’ve played 'em for hours straight at a time. Maybe it’s the drier than a bone air out here in phoenix, and probably is, but the only problem I’ve encountered with those is the fipple being soaked with that mysterious ‘saliva’ stuff or whatever it is and wants to be called.. Those are funny whistles, cause, when I do play them for hours straight, the “saliva affect” just beads up and runs down the barrel of the whistle.. Kinda gross when you’re playing to a song at that time, and you get this nice cold wet pool in your lap… 
-Eric
Some individual whistles do tend to bead up in the windway more than others, and while I don’t make it a practise of bulk treating whistles with chemicals, if your particular whistle needs the treatment, I’d say go for it. You have the control over what you put on and can wash out anything you don’t like or which doesn’t work.
While I’m here, I might just say that the aluminium syn whistles probably benefit from an occasional clean out and rinse with soap and warm mater. I’ve noticed a couple of whistles reacting to saliva and building up a white deposit, I assume aluminium oxide, so the occasional clean out will help.
Cheers.
Well, as of yet, neither of my Syn whistles has a clogging problem at all.
I have done the treatment to other whistles, though, and to wooden recorders, and it seems to always fix the problem.
–James