One other thing. After a few weeks of playing the NS, I noticed a lot of pain in my left thumb and across my wrist. I thought about it, and realized that because there is no upper bout to get in the way, when I moved into the higher register, I was not moving into a thumb position, but was keeping my thumb behind the neck as I moved up - putting my left hand and wrist into a crimped position that pulled my tendons in ways that were truly unnatural. I corrected and started using proper thumb positions again, and the pain abated. Maybe reading this will spare you the same problem.
Rick B.