Well, it appears that there
are adapters to use an SD card in a CF slot.
That's the good news. The bad news, for me at least, the adapters are designated as Type II format, and the D700 is a Type I format.
While there is a way to strip the cover off the Type II and fabricate its use in the D700, there are some possibilities of damaging the camera.
Reconfigure SD/CF adapter to Type I on Vimeo
I'll pass on that option.
Maybe in the future, a Type I adapter will be available (though I doubt it).
"It is doubtful that an SD to CF Type I adapter anyone will take the trouble to create one. Type I spec is only 3.3mm thick and full sized SD cards are 2.1mm. That only leaves 1.2mm for the top and bottom shell and stuffing in contacts which are fairly large on an SD card. Another challenge is the CF pins are close to the full height of the Type I spec. Looking at my Type II adapter the SD slot consumes nearly all the volume beyond the CF pins so I think that the extra height of the Type II spec is used to get the contacts for the SD card in there."
Thanks to all that stayed on topic with constructive comments.