Mujitsu and Tairaku's Shakuhachi BBQ

I am the owner of a bamboo nursery and of course have an interest in all things bamboo.  I have been contacted by someone who makes Shakuhachi flutes wanting to buy blanks.  I normally only deal in live plants but have a large grove of P.bambusoides and access to several other groves.  i am interested in offering shakuhachi blanks but haven't been able to find much information about the raw material. I do know that P.bambusoides is the traditional species used.  i know that bamboo canes need to be at least 3 years old or more befor harvesting but that's about it. How can I learn more about choosing and harvesting bamboo for use in  making shakuhaci flutes? The craftsman who contacted me tells me he has trouble finding quality blanks.  I would love to be a reputable resource for the shakuhachi craftsman - I just need some information!  Any advice or help would be appreciated.  Thanks
Jim