I purchased the "Thumb Stop" that NS sells. It's the silliest, seemingly overpriced, little piece of wood you can imagine. Regardless, I am glad I purchased it. I personalized it a bit as I put it at the Db position, as opposed to the traditional D or Eb position of the Neck Heel. It has been a game changer for me in able to play in the middle positions of the neck and being able to navigate the fingerboard while reading music and not having to look at my fingers. Perhaps it is not necessary if you're playing the NS as a big fat bass guitar, looking at your fingers, not caring about thumb position, etc. But I want to approach study of electric upright so as to have as seamless as possible transition when playing Double Bass. I think that having the thumb stop to mimic the neck heel is another means to that end. My two cents on the matter.