New v10sport race rudder

Hi
Anyone knows how much one gain with the race rudder if one average 10 km/h?

Not sure what rudder you are talking about, it come standard with a universal rudder so I assume that is not what you are talking about. The other rudders are the weedless and the surf rudder.
The smallest rudder will give you the quickest ski as there is less resistance but still turns the ski well enough in small runs. The surf rudder is designed for bigger runs and is very responsive especially on the Sport.
The standard (universal) rudder should be ideal for both situations.