With a sharp focus on the goal of the work, careful planning involving key people, and a focus on providing the group with just the structure, information, and process they need, significant work can be done in just a couple of hours. Bill was excellent at getting real work done with a diverse group of managers in a 2 hour session. Everyone was heard, and no one was allowed to dominate. We stayed on track and produced useful results on time. I was impressed.
Many people think of effective group work as limited to small groups.
Yet sometimes you know you really need to involve a large number. Call if this is your situation.