I'm happy to report that I've found a path to tethered shooting for the D800, albeit a clunky one.
Nikon's Capture Control 2 has finally been updated to Version 2.11.0, which accommodates the D800.
As to the issue of long cables to use in the studio, I attached the USB 3 cord that came with the D800, to a 15-ft. cable from Iogear which is said to draw power from the computer, if I have that correct. It is Iogear Model No. GUE216, available through B&H. This results in a USB 2 connection, but that's OK with me.
The clunky part is that I still have to process my shots in Light Room. So I use Capture Control 2 to bring a NEF into a watched file on the computer. Then I manually open it with Light Room and go about my business.
Any wisdom on how to automate this hand over would be much appreciated.