Laurie: Yes, I have done OS in three hours (actually less, however it was a group that was familiar with OS). My experience has been that you just have to be careful to watch your time for the opening and the sessions. I like to use the US West Communications video, with Harrison, for new comers. It gives them the feel of OS pretty quickly.
I would then allow 45 minutes for the opening (including the video), and then two sessions 45 minutes each, which leaves 45 minutes for the closing. If there are not enough issues on the wall for two meaningful sessions, then combine them into one longer session. The main thing is have a plan, and then be prepared to change it in ways that make sense. If you aren't uptight, then the group won't be (usually). After all, think about what's the worse thing that could happen. Then compare it to everything in the cosmos, and it doesn't seem all that bad. Have fun and good luck. Dave Koehler Peoria, IL USA