May be we could we do that another way..
As your circle has its own purpose, and as you have a metrics section in the Tac Meeting process, you could juste define relevant metrics wich mesure the progression of the circle toward its purpose... So the metric review will give you the picture you need.
If you need thougts about the way the circle may reach its purpose, as Paul suggests, a proper solution could be to set a strategy meeting, smartly designed for this specific topic.
Separating stategy space from tactical one will help the facilitator to maintain a high level of energy and the smart pace of the Tactical meeting.
Hope that helps,