Test day:

First with seat harnes and 25 cm fin. More power but less upwind. Two good runs with 35 knots

Then  waist harnes and 25 cm fin. More upwind but less power. Too lift. Two runs with 34 knots

Changed again to waist harnes and 23 cm. Better control. Best top speed: 35,57 knots.

Finaly seat harnes and 23 cm. The worst, power but not enought lift.

4kg extra

Test day:

First with seat harnes and 25 cm fin. More power but less upwind. Two good runs with 35 knots

Then  waist harnes and 25 cm fin. More upwind but less power. Too lift. Two runs with 34 knots

Changed again to waist harnes and 23 cm. Better control. Best top speed: 35,57 knots.

Finaly seat harnes and 23 cm. The worst, power but not enought lift.

4kg extra

Test day:

First with seat harnes and 25 cm fin. More power but less upwind. Two good runs with 35 knots

Then  waist harnes and 25 cm fin. More upwind but less power. Too lift. Two runs with 34 knots

Changed again to waist harnes and 23 cm. Better control. Best top speed: 35,57 knots.

Finaly seat harnes and 23 cm. The worst, power but not enought lift.

4kg extra