Sinking the leeward rail
Tony, thank you for your hints! I never really expected I might have to go into an 8.5 or larger sail with a short-board, because I fully agree with you : with a long-board, a 6.4 was quite enough, even overpowering and difficult to handle at times! But your suggestion makes sense and I'll see if I can put my hands on an 8.5 or so.
I just wanted to make sure, though, which one is the LEE rail . I know it is the down-wind rail, but since we don't sail facing the wind, rather with the wind coming from behind or laterally, at different angles, the LEE rail would have to be the one opposite to the side you are standing on and I imagine it is a bit ackward to shift your weight to the other side of the board in order to sink that rail ! Were you perhaps thinking of the rail RIGHT UNDER your feet when you are standing on the board( which seems a lot easier to sink, just by leaning outward and pushing your feet against the edge ) or were you really thinking about the opposite one? Please tell me which one you meant, regardless of the name !