Dear Jeroen
As I can imagine buying a Monette isn't an option for a lot of people (me included)
Your choice of a Bach 1 1/2c with a symphonic backbore is a good one. Most manufacturers use the Bach as a measuring post for thier mouthpieces. If you dont want to try a Monette mouthpiece. I think youre on the right track! Good luck!
Rick AKA Trumpet Man