RE: thanks very much for your time and answer
I was just about to rephrase my question to make it less work for you. A great response! I am heavier (79 kg) and probably taller and often do use 6m sails on waves in conditions where there are usu. only surfers or very skilled light wind purists. I have found that the 83 does not work well for me with a 5.8, though it might with a bigger fin or different sailor.
The FSW behaves almost exactly as you indicate, and experience with the E83 or a last generation rockered wave board makes it possible for me to tell.