I did it, for a strength challenge. It consisted of almost 20 exercises. Each one rewarded with points.
I started managing this session with the 2 women 5 months before the Day. It doesn't take that long, but it does take a lot of emails to coordinate.
If they don't know each other, it's better to choose 2 women who are fun, or at least 1. If the atmosphere is too competitive and tense, it can get stormy. They may be far from home, tired from their trip. They probably don't want to have travelled for peanuts.
So, be kind, accommodating and clearly describe what you expect from the session and what they can gain. Even for the looser.
