Maximum size is 7.0 m2. In my mind for my weigth i can't match perfectly the 3 sizes 5.5, 6.2 and 7.0 on a unique board.
With the 97 i think normaly i am easy with 6.2 and 7.0.
With the 90 i think it is ok for 6.2 and 5.5.
My quiver will have those 3 sizes 5.5, 6.2 and 7.0.
Having in mind the size i prefer is 6.2 in 20/30 knots.
I add i make windsurf in south of France by off shore wind( Fos sur mer, Saintes Maries de la mer ) , spots like Gruissan in fact