You're misunderstanding the problem I was addressing, Harry.

The problem - having a start when a previous class is going the gate (when the gate is located directly upwind of the signal boat), thus creating significant interference between the two classes.

The "old school" solution when you've got more than four classes is to have the start/finish line mid-course, so that boats going through the gate don't interefere with classes still starting. However, this type of course is harder to manage in shifty wind.

Typically, we try to have 12 minute upwind legs on a 45 minute race. Downwind legs take less time, especially for spinnaker boats and the difference is more pronouced as the wind velocity increases.

With 5 minute "rolling" starts, you can easily get 4 classes off without interference at the gate (gate directly upwind of the signal boat). If you have a significant shift, you can signal a change to the boats starting with the "C" over class flag and then to the boats already on the course with a "C" flag at the gate. It requires you to be on your toes as a race officer, a reliance on your timer to keep things going in the "back" of the signal boat and a mark boat operator that knows what they're doing.

It is cool when you can pull something like that off - and all the competitors get it.