bass mp with small shank

[rizzo67]

Today there was a mouthpiece in the post I wanted to try on my bass trombone.
Nearly the same as I use now, the JK 1BK, but with a smaller throat. Unfortunately the JK 1A has a small shank, not as described the 12.5 mm.
My first thought was to send it back, but then I tried it on my Yamaha 645 and in the low range it worked well.
Normally I play a Bach 6 1/2, but last week I spontaneous had to play bass an it sounded quite shallow.
What do you think, is there a reason to keep a bass mouthpiece for a medium bore trombone?

[BGuttman]

Can you play your upper register in tune? If so, it should be OK.