Each rainbow cup has had a different structure to attract different players.
The first 2 RC's were 4v4 tournaments.
RC III and IV tournaments were - 12 teams of three with open ratings.
The last tournament was also 12 teams of three, but.. sub 1800s.
This tournament with only 8 teams of three. .
was meant to have the highest average rated teams to date.
(plus be shorter, time wise each day)
It's a gamble to host a tournament with too many teams and
not have it fill up properly,
which would make for unbalanced teams.