Meng was scare to use his 10.5 at one time when the wind was honking at 20+ knot in Malaysia....but he is right, pratice + ur guts make u a stronger man.
For ur weight u definately can do more than this. I am 187cm/92 kg sailor with about 2 years plus experience on formula board. So far i always use 10.5m for the wind range u mention(But b4 that i not even can hold on a 9m during monsoon season)but prefer on a 66cm fin. . My next sail is 11.6 only use up to around 15+ knots then i overpower like a gal..
It's a pain in the ass brother, really suffer at 18 knots and up but it is also a "FUN" and crazy things to do when the rest are using smaller sail yet they are over power. It also depend on the sea condition, when it is too rought i prefer to sit and watch other sailor over power on their smaller equipmen...
Happy sailing.