Haven't done it, but here an excerpt from the peleton sports forum:

"if you do the Coluzzi-Waterfall ride on Saturday and find yourself "riding solo" in the bunch for more than a minute, then you will be told in no uncertain times where to go ([edit] ie. go to the back of the group[/edit]. While I do not condone this rudeness, the effect is that the bunch rides in two very neat lines (except for the "race" between Waterfall and Sutherland) and averages 38-40kph for 80km every Saturday."