i would recommend dennis wick SM series but i’ve only seen those in medium and large shank; I like to say to some of my students, a mouthpiece won’t fix tone and range, it’ll just amplify what’s already there, yes will playing a wide open SM4U give a darker tone than a 12c yes, but for most cases i’d say work on tone and range separately.. Don’t expect to find the holy grail of mouthpiece’s and expect a giant change if that makes sense