I recently recieved a CPVC Bb whistle from Mack Hoover.
The whistle is very attractive…white with a brass tuning slide…and nicely finished.
It is well-balanced across both octaves and doesn’t require one to blow one’s brains out to play the high end. Tuning is also very good.
The tone is very warm and rich and fairly pure without being boring.
It’s not too bad on clogging as long as you don’t play like a sissy.
Mack’s whistles have a reputation for being quiet and while this whislte is not as loud as my Water Weasel Bb it has plenty of volume.
I had a narrow-bore brass hi-D of Mack’s some time back and quite liked it…now that’s a quiet whistle! The tone was so sweet and pure…it was an utterly delightlful little rascal to play. I have a strong affinity for hornpipes which my wife doesn’t share. :roll: The Hoover narrow-bore was quiet enough to play hornpipes at night without risking the dog house 
. I sold it in a fund-raising frenzy to buy a flute and have missed it. 
The only thing about the Hoover whistles that is a little odd is their peculiar dislike for playing C-nat with OXXOOO. However, C-Nat can be half-holed or played 0XX0X0. Personally, next time I have Mack make me a whistle I’m going to try to talk him into drilling a C-nat hole in the back.
Mack is a terrifically pleasent fellow to work with.
Thanks Mack and keep up the good work! 
Doc