@norman I have contacted Mack Hoover about a Bb, but as per your statement, "...it takes a whisper of breath to play it" I have backed way off my Dixon Bb and it is beginning to sound a lot better.  Us "newbies" take a while to get some of these things learned.  However, because you can never have enough of any kind of instrument, I may still get a Hoover.

My "go to" tune when trying out whistles is "The Water is Wide".  I have it down enough to play it on different whistles to get a good idea of how they sound and play.

Paradigms, both of my Hoover's are phenolic resin. Check out his web site. Lots of interesting information and sound clips.

@norman is your Hoover a brass or composite whistle.  I would like to have a nice playing Bb and the Dixon brass isn't doing it for me...course I'm really a newbie so that has to be taken into consideration.  Love the D carbon fibre from Eric the Flutemaker.

I have a Hoover Bb that takes less than a whisper of breath to make sing. I play at hospitals and assisted living centers and all my whistles are much too loud there.

Mack voiced a D and the Bb so quiet that they are perfect for my special folks. In fact, if I forget and play them like my Dixon I almost burst a lung from the back pressure. However, played softly they have a sweet, gentle sound.

@Papasims, I like the tone of the Dixon brass "Trad" models.  I have them in high E, D, C, Bb, and low G.  They all sound pretty nice except the C, which I can't stand to play and takes way too much breath for very little volume. 

I think there's a point where a maker has to switch to a bigger diameter tube when working their way down from key of high D.  Sometimes it seems to be at C, sometimes at Bb.  The Dixon Trad brass is a bigger diameter then the high D, the same size tube as the Bb.  But the Bb works and sounds lovely for me, whereas the C requires way more work and doesn't 'sing' for me no matter what I do.  If you have trouble on the Dixon brass Bb then i advise you to steer clear of the C!  Of course any larger whistle is going to require some extra care in finger placement and breath control- I find larger whistles take some getting used to. But if I spend an hour or so playing one, I always wind up making it sound better than when I sat down with it.

The more I jump around between my various whistles the less I can get better at playing a particular one, because each whistle is different. But it's such a hard choice to purposely stick to just one or two whistles for a long while, when one has a dozen fun whistles in various keys and materials to grab.... 

I now have a Tony Dixon brass Bb.  It's giving me fits getting the breathing right and the holes covered correctly.  Slow and deliberate is the course to follow but I want to play it perfectly right now.  

I'm always surprised at how the tiniest air leak where your finger covers the hole can completely ruin a note and make it sound just horrible!

I believe  the "screeching thing" is caused more by mis-fingering a hole than by breath. With practice it becomes less an issue. Breath control is harder to develop, particularly when trying to blow the whistle into tune. 

Certainly was true for me in the very beginning.  I have enough whistles at this point to have realized that some whistles are more quick to jump octaves than others- I found that to be both a curse and a blessing for a beginner!  Regardless of individual whistles though, logic dictates that the more breath control you develop the more you can adapt to various whistles so you can better control that 'jump' wherever it's located in the particular whistle.

I too have experience only with stringed instruments before this.  I feel your pain!  

Absolute beginner on the whistle.  Used to string instruments and playing by ear.  I'm having to learn a whole new system here of finding my notes but it's coming around.

Does it take a while to regulate your breathing so you don't jump octaves or do the screeching thing?