The duo had a first and a fourth in their two races overnight to move 10 points ahead of second place. They now head into the gold fleet racing for the top 25 boats with four top-five finishes in the five qualifying races.
"The first race of the day for us was especially good, coming from 14th place at the first windward mark to take the win," said Tuke.
Marcus Hansen and Josh Porebski are eighth overall following a 10th and sixth overnight.
Jo Aleh and Polly Powrie are creeping up the leaderboard in the defence of their women's 470 title.
A fifth place finish overnight has the Kiwi duo up two places to fifth overall. The defending champions have 18 points after five races and sit amidst a tight bunch on the board -- the French pair in 2nd have 16 points, with the crews in 3rd and 4th both sharing 17 points with the kiwis just behind.
Sam Meech is the best of the Laser sailors in 10th with Sara Winther 12th in the Laser Radials. Jon Paul Tobin is 12th in the men's windsurfing and Natalia Kosinska 21st in the women's fleet.
