I managed to try a Monette B4LDS1-LT mouthpiece (classic) and it felt too shallow and tight. The equivalent bach mouthpiece to that would be the 3D.
The comparrison im after which i know isnt the best way to look at it as its different but bare with me... is...
I tried a Stomvi 3C Flugel Horn mouthpiece which felt BEAUTIFUL. Didnt feel TOO large and didnt feel too tight, it was just right. I played all my notes from low to G above staff very comfortably, i was like "in the zone", it was just part of me.
To get the trumpet mouthpiece in something of equivalent diameter/depth of a flugel horn 3C, what would that be?
And what would that translate to in a Monnette mouthpiece? Jason figured a B2MS3 which is a bit deeper than the B2S3.
Kinda need to know the depth and diameter in mm of a 3C flugel Horn mouthpiece to then find which trumpet mouthpiece has the closest mm in the 2 dimensions I guess.