I know its an older thread, but I am chiming in anyway. You can also try a Wick 6B (Steven Mead or traditional), if you like the Bach overall. They are a bit roomier. The traditional 6B is an improved 6 1/2 with a better tone and low register. The Mead version has a different cup shape and rim contour that make it feel even a little more roomier than the traditional 6B. I have enjoyed using the Karl Hammond mouthpieces. The 13ML is like a 6 1/2 with a deeper cup, and with the bowl to funnel shaped cup that is his standard design, really helps the upper register. My $0.02.
Raul Escobar
1985 Willson 2900BS, Hammond 11L
1974 King 4BF Silver Sonorous, Hammond 12ML
1972 King Duo Gravis, Hammond 20BLL