Hi Mike,
100 posts? I had a look at the rolleiusers Yahoo group that Sanders mentioned. The latest message is numbered 19,058, and there are 10 or 12 posts a day. Nothing much to do with Rolleis though.
I am a member of the RUG mailing list, and as you say there is some useful information in there. The few times that I've seen questions about the SL 66 there has been little response - photo.net seems better. In general, I think that open groups fare better than brand-specific groups, particularly from those of us who are uncomfortable with brand identity (I won't go as as far as saying 'mutual admiration societies'). I get a significant number of email queries about the SL 66 from my posts on photo.net, possibly more than the number of threads on the SL 66, so I suspect that there is plenty of interest.
Best,
Helen