Hello Fin 66!
I found for my F162 as best mast base position with CR08 11,0 AND 11,7 "-2CM" measured back from the middle of the mast track not counting the insert hole (184cm 90kg). Additional I rised my boom 3 cm up from my normal position. All straps back. The fin thing is most important. You have to find a fin which gives you enough power riding the board nearly plane and not on the leeward edge. The R13 only works using the leeward edge. So forget it. Try something powerful and big. Use a cutted one with a wide powerful tip, soft flex and nearly no twist ( thats the only secret os Kashy).