Thanks for comments everybody. LK and kennatt, you sound like you have some experience on the subject? Actually, I found an older post, where kennatt said that "9 meter full cam race sail" worked "just about ok" for him on a similar board... maybe me being 15k lighter would help here? This is actually quite in line what LK said... Also, isn't the code red supposed to be a light sail, or is it just "light feel"?
Supposed the 9.0m2 sail is too big for the board: what does it mean/how does it feel? More difficult to uphaul? More difficult to sail?