I would also favour (at least) 3 races per day and having them last for about 45 min each.
It is a whole lot work putting the boat and bouys out (and retrieve them) for only 2 races per day.
Wouter
I'd suggest slightly longer races; aim for first finisher within the hour so all are finished (hopefully) within 75 mins and then re-start within another 15 mins or so (hopefully again).
