I know that you probably do not have a lot of experience with the biggest S-Type (137), even though you may have something to say.
I have a problem with spinout on S-Type when going upwind, in fact I induce the spinout by changing radicaly from slight downwind or haflwind course to sharp upwind (I like it as I can lay myself over the water and sheet in completely).
What do you thing about the fins size (I have now the standard 480 freeride flow). And I was sailing only 7.0 (currently my biggest one) at 15 to 22 knots.
Ian already gave me some tips but you know... the more people the better.
If you have a time, while good mooded, you can check the thread in Team Forum....link below.
Thanks a lot.