I was shooting dome product shots yesterday and discovered my SB-26s will fire in slave mode with my SU-800, note that's the SU-800, not the SB so it's not firing from optical slave. It must pick up IR signals. No controls of course, all manual, but still pretty neat.
#1. "RE: Cool discovery regarding SU-800 & SB-26!" In response to Reply # 0
When you say 'slave mode', do you mean connected via a PC or TTL cable? Or using SU-4 mode? If the latter, have you actually tried taking pictures using the SB-26s? I suspect they are firing during the preflashes and not during the actual exposure.
If the SU-800 has PC and/or TTL terminals then you can connect a SB-26 with a cable and have it fire during the exposure (I've done this using my SB-800 and SB-28); although, it will not fire during the preflashes; so, the camera meter will not take into account the flash output of the SB-26s when calculating exposure.