Udo Hessels, Marcel van de Veen and Mischa Rossen continued their strong regatta as they won the first race of the day and came third in the second.
That left them 10 points ahead of Aleksander Wang-Hansen, Marie Solberg, and Per Eugen Kristiansen of Norway on the overall leaderboard.
But the standings were altered still further following the end of the day's sailing, as the Norwegians were disqualified in the fifth race of the 11-race series for an infringement, sending them out of the second spot overall in the class to sixth.
France's Bruno Jourdren/Nicolas Vimont-Vicary/Eric Flageul are now in second place with Colin Harrison/Jonathan Harris/Stephen Churm in third.
In the other classes, Great Britain's Helena Lucas sits top of the Single-Person Keelboat (2.4mR) standings after recording two victories on the south coast today.
After a two-hour wait for the breeze to arrive in Portland Harbour, the 37-year-old opened up a nine-point advantage at the top with a double bullet - Sailing terminology for victory - in today's races.
Lucas is now favourite for gold with just five races remaining but will not be taking anything for granted.
She said: 'I couldn't have asked for more than that today, I'm just really, really pleased. But I'm absolutely not thinking about where that has left me.'
Germany's Heiko Kroger is Lucas' nearest rival, while Thierry Schmitter of the Netherlands and Frenchman Damien Seguin are also in the chasing pack.
In the Two-Person Keelboat (SKUD18), there were two close races.
In the first, Great Britain's Alexandra Rickham and Niki Birrell finished first, with the Australian crew of Daniel Fitzgibbon and Liesl Tesch holding on to second and the USA crew of Jen French and JP Creignou finishing third.
The same three teams hit the front early in the second race, but this time Fitzgibbon and Tesch prevailed to win, with the USA crew second and Great Britain third.
That means Australia lead the fleet by a point from Great Britain in second, with USA a further point behind in third.