Got this question via the Lightscoop web site:
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"The Lightscoop appears like it would also be beneficial when the Nikon's pop-up flash is used as a controller for external CLS lighting. The problem with the usual way of doing this is that the direct preflash from the pop-up flash in Commander mode makes many subjects blink during the actual exposure, even when the pop-up is set to "—". It's my understanding that the Nikon SG-31R IR Panel will work to eliminate eye-blinking from the preflash when used this way, even if the front of the panel is covered with black tape. Have you done any testing to see if the Lightscoop works well for this purpose?"
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Ran a couple of tests, and, YEP... the Lightscoop does work for this purpose. Didn't have a subject likely to blink, unfortunately... but here's a quick shot with the SB600 held off camera, fired by the pop-up flash with a Lightscoop in place. It ain't art, but no cables, additional slave units, etc.