Hannah Mills and Saskia Clark (GBR) were well placed for gold but it slipped from their grasp when they finished last in the medal race and USA's Anne Haeger and Briana Provancha stole the overall victory.
Aleh and Powrie have now had seven podium finishes at the major international regattas in the women's 470 class this year, including victories at ISAF Sailing World Cup Miami, Princess Sofia Regatta and they claimed the Women's 470 European Championship title.
The men's and women's 470 World Championships are on in October in Haifa, Israel.
Josh Junior romped away for a medal race win in the Finn finale.
Lying fifth going into the race, the win wasn't enough to alter his overall position and he wraps up the regatta with that as his final result.
Gemma Jones and Jason Saunders went into the final double-points race sixth overall, and a decent final race saw them lift their placing to record a top five finish in the Nacra 17.
Peter Burling and Blair Tuke took 49er gold to continue their domination of the class.
Alexandra Maloney and Molly Meech finished fourth overall in the 49erFX.
Men's 470 pair Paul Snow-Hansen and Daniel Willcox were back on the water sailing one race in which they placed 13th. Their week was interrupted when Willcox had to sit out on a day of racing on the doctor's recommendation and they conclude the regatta in 20th overall.