According to Rich Holmes' "Normal Person's Guide to the Morris", a side is: "(1) A morris team. (2) Enough of a team to make a set."

Both morris teams I've been on (berkeley and Apple Tree) have numbered around 30 at their high points, but even then on any gioven day (depending on the nature of the event we were planning to attend) might be able to field only a "side" of eight or ten -- enough for one set (6 dancers in a set, for most dances) and a few spares, but NOT enough to ensure that nobody had to dance two dances in a row.

Hope that helps.

Claire