Hi Enrico, the Kode 94 is a good choice I think.
But before buying another sail, practice with this new board and your 4.7 Core sail at 30+ knots in more flat water conditions (side-shore to off-shore on the sea or preferably on a lake) to get it planing. You've got to realize that this board is a full sinker under your weight and depending on your experience with sinkers it will be even more difficult and technical to get it planing in the beginning. Afterwards you still can decide about another sail. On-shore heavy wind 30+ conditions on the sea are the most difficult & technical conditions for windsurfing. It needs a lot of practice. Take a look at real heavy on-shore conditions in Sylt/Germany last year and enjoy.