Polish sailor Pawel Tarnowski adapted to more gentle conditions and excelled during sailing at the World Cup Series in Gamagori, Japan.
A stiff northerly breeze at least picked up to allow participation in all eight Olympic sailing events.
Today marked the final opportunity for both the Men's and Women's Windsurfer (RS:X) and Men's and Women's Skiffs (49er/49erFX) fleets to book their places in tomorrow's Medal Races.
Tarnowski, 23, shone in the Men's RS:X, improving on his third place in the first race, with two victories, meaning he climbs to first place in the standings with a one point advantage over China's Mengfan Gao.
Tarnowski beamed: "Finally, we could get some good racing in, having waited for long periods of time this week.
"We had three very hard races with a lot of pumping, a lot of wind changes and gusts.
"It was really challenging but I was able to gain some nice points."
As for contending with the nerves of competing in a Medal Race, Tarnowski added to World Sailing: "For sure, Medal Races bring more pressure than the qualifying series.
"We will prepare well, like we always do, and hopefully we get some nice wind.
"I would love to have another day like today."
The Women's fleet also completed three races on their final qualifying day.
Japanese duo Fujiko Onishi and Megumi Komine sit on top of the leaderboard on home waters.
Hei Man H V Chan, of Hong Kong, currently lies third.
The 49er and 49erFX fleets also have their Medal Races tomorrow, with sailors pushing hard to achieve their highest possible finishes.
Dylan Fletcher-Scott and Stu Bithell lead their British teammates James Peters and Fynn Sterritt by five points, with Polish duo Lukasz Przybytek and Pawel Kolodzinski third.
It remains tight at the top of the Women's fleet with just four points separating the top three pairings.
France's Lili Sebesi and Albane Dubois lead by three points.
Sayoko Harada and Sera Nahamatsu (JPN) lie second, with Victoria Travascio and Maria Branz from Argentina, third.
The other four Olympic sailing events will decide their Medal Race fates tomorrow, the final day of qualifying racing.
Pavlos Kontides, of Cyprus, leads in the Men's One Person Dinghy (Laser) continuing his recent good form after winning the class World Championships earlier this summer.
New Zealander Sam Meech trails by ten points and Britain's Lorenzo Brando Chiavarini is a further 20 points behind, in third.
In the Women's One Person Dinghy (Laser Radial), Greek sailor Vasileia Karachaliou holds the lead ahead of Josefin Olsson, of Sweden and Belgium's Emma Plasschaert.
Rio 2016 Men's Two Person Dinghy (470) silver medallists Mat Belcher and Will Ryan, of Australia, have dominated the fleet after six races.
New Zealand's Paul Snow-Hansen and Daniel Wilcox sit second with Japan's Tetsuya Isozaki and Akira Takayanagi in third place.
The Women's Two Person Dinghy (470) fleet managed two races on day four of the event.
Poland's Agnieszka Skrzypulec and Irmina Mrózek Gliszczynska led from Swiss duo Linda Fahrni and Maja Siegenthaler with home favourites Ai Kondo Yoshida and Miho Yoshioka in third.