Thank you Roger for your informative information!
I hadn't thought about going smaller in board size like the Carve 111. I admit your proposition is tempting. But I won't be able to test these boards beforehand. Therefore I will play it safe and choose a little wider board for more stability. Seen your explanation (the smaller the better for my weight), I will probably choose the Carve 131.
I begin from zero again with my equipment. Can I buy only one sail for the wind range 11-20 knots? Or will I need 2 sails for not overpowering my arms in the upper range? (For the Carve 131)