I haven’t played a carbony, but I have played a clarke sweet tone. And it also has a really loud and harder to hit high B. Which may be a side effect of conical whistles; The bore is larger for the high notes. Once I saw a small bore carbony on sale on facebook and I asked the guy if it was a quieter whistle and he said no its still loud. So I’d expect the high B on the normal bore to be louder and harder to hit.
That being said, you should be able to change your technique to be able to hit the high B. You don’t really want to just blow harder, you want to blow faster air. Which might not make a lot of sense at first. But the shape of your mouth can effect how fast the air is. An example. Make a big ‘O’ shape with your mouth, and blow. You can blow as hard as you can and the air speed still isn’t going to be that impressive. If you suck your cheeks in and press your lips together and blow through a tiny hole, you will get way better air speed, using way less air. I didn’t realize how big a difference this made until I got my Reyburn low D. Its noticeably harder over blowing than my MK. So trying to hit the high B, by just blowing harder without changing my mouth shape, pretty much cant hit the high B. When I first got my MK even, I was getting headaches playing it. I’m assuming I was once again blowing wrong. Because now I find it overblows very easy compared to the Reyburn.