Hi Jerry, I've been thinking of getting one of these. How has it affected your battery life?
I've also been thinking of their units that have their own battery. But it is larger than the one you linked.
https://www.solmeta.com/Product/show/id/24
It can apparently also record a track file while the unit is on, but not attached to the camera. My understanding is that the track file could be added later to LRc or Nikon Studio later if the time is synchronized with the camera.
Thanks in advance for your experience with this. If I can satisfy this issue adequately, it will mean z8 versus z9 when I go mirrorless. I'm still shooting a d500.