Lightwindsails on Isonic

Hey Guys,
i bought an older isonic (121/75/2010) and i am curious what you would ride in light wind conditions.
I thought the 8.6 would be the obvious choice for the 75cm width, but i'd rather have a 9.3 for early planing.
What combination would you choose?
Can you go at the very limit of the 9.3 at the upper wind level?
greetings Arvid