jn1 said..
Interesting harness design. It looks like a waist harness, but is positioned on the bum ?
To be honest... modern low profile seat harnesses can already be ridden as soft waist harnesses if needed either with the leg straps undone or very loose to prevent it from riding up. Maybe not for kitesurfing because they are a bit too soft but for windsurfing it'd definetly work just fine.