Hi,
Backpressure is a very subjective parameter, some always want more, and some like less.
I am a gentle person and like fluency and openness but with a feedback, so
no special diaphragmatic pressure is needed like in flutes and wide bore whistles, the resistance of the airflow is noticed in the mouth.
The c natural is best achieved by using 0XXX00.
Of course wide bore models, different keys etc. will be available.
I thank you all for the kind comments,
Gal.