Hi, I play a Bach 42b with the typical 5g mouthpiece. I just joined my local symphony and I am playing some bass trombone parts. I feel like I need a little more cup room. I am a big guy, relatively thick lips. I have never played on anything but this mouthpiece but am willing to try. I have a harder time hitting the low notes. When I play down to them I can, but not when I need to hit them right off the bat.

Any suggestions? What about the 3g?