its just not that low of a dynamic - brass tone changes dramatically from pp to ff - it's not just a matter of volume. I don't think I need to explain the irony of your user name asking me that.That's really good to know. Why not just make 30 your minimum then and use it like that to get realistic results?
But to clarify:
you can reduce the volume of a horn playing at fortissimo all you want, it'll never sound like pianissimo
you can increase the volume of a horn playing at pianissimo all you want, it'll never sound like fortissimo
CSB has absolutely stunning crossfades of the higher dynamics - but very little ACTUAL low dynamics to work with, sounds dull and low volume - rather than golden and mellow.