I just began testing the medium and large HBC caps on my Adams. I'll save my own impressions for a bit (and I'm still fussing around with things), but here is a video where I did a comparison back-to-back with the Adams standard 4th cap, the HBC medium cap, and the HBC heavy cap.
Of course the sound output is not the only relevant factor; the "feel" is also involved. And even with sound, when I record in the basement I have to use close-mic'ing. Normally when doing that I add some reverb, but this recording is untouched. So you are hearing what comes off the bell, but you might hear a different effect in a large room. (No large room is available to me right now.) Nevertheless I think you may hear a difference, and that difference seems to match what I hear from behind the mouthpiece.
See what you think, and please comment!
https://youtu.be/LNVoANFHuHc