Does anyone else here play on a bobby shew jazz mouthpiece? It's the yamaha one which is similar to a 3c. I have been playing it regularly recently and can't quite get my head around it. I love the sound I get from it but i have to really fight to keep in tune between 3rd space C and the F# above that. Tuning is fine throughout the rest of my usable range up to F above high C. Any ideas what could be causing this?