The round-robin format has been used for the H-16 North Americans for many years - anytime there was more than 65 boats.

The competitors are "seeded" by the organizers in consulation with the class - an admittedly subjective process, but good enough for these purposes. The competitors are then divided into 4 groups, with every fourth seed going to a specific group. That way you end up with four groups of roughly comparable competitive depth.

Races are run in sets - two groups race together in two separate starts. For example:

Set 1 - Start 1 - Groups 1 & 2; Start 2 - Groups 3 & 4
Set 2 - Start 1 - Groups 1 & 3; Start 2 - Groups 2 & 4
Set 3 - Start 1 - Groups 1 & 4; Start 2 - Groups 2 & 3

Ideally, you'd like to have an even multiple of 3 sets to ensure that everybody races against each other the same number of times, but it doesn't always work that way. As long as you run in sets, everybody has the same number of races. After about 6 sets, positions are pretty well determined and you can make a cut.

I don't know if this is the method they are using there, but it has worked well for us for many years.