I've had a bit of experience at this sort of thing, Admin on one forum and moderator on another. You can NEVER tell what might work and what might not. I've been through the situation of people clamouring for a particular sub forum and much discussion and finally creating it only to find, after a short burst of activity, it's lucky to get half a dozen posts in a month. Maybe a sheath forum would do really well, but just because plenty of people think it would be a great idea, doesn't necessarily mean it will. Not meaning to put a damper on the subject, just pointing out some realities from personal experience.