Hi marvin377 & raffig,
This is my tips as Julien Quentel who wins the European. This is not to used over 15 knots to give very good result, over we go to other fins.
Mast track position : A bit behind the middle of all the mast track
Phoostsraps : All of them in the back and outside
Height boom : eayes
Harness line : I have trim harness line, but definitely same longer of my arm. Sorry my english is not perfect but you take your boom and harness line arrive to hook your elbow
Trim of the sail : normal
My height : 186cm
My weight : 85kgs
Hope this can help.
All the best