I have 82 kg and a Ozone reo 12m with a sector V5 54 wide, three fin setup and they are more slalom fins not race.
I think you can manage the 10 kts with a 4 fin setup, and 28m lines...but the kite will be slow, not that you need a fast kite ( fast in turning or sining) but you will need technique , also in those low winds( for a 12m) you should train the backloop/ downloop with jibing , this will give you a steady pull through out the jibing maneuvre because it will place the kite where you need it, coming out of the jibe thus keeping the speed, where the regular jibe you will have to steer the kite one more time down and up, in that moment you loose the speed in the board ( in 10 knts)
be sure to let your kite "breathe" meaning: avoid pulling the bar in...keep a open kite in light winds, even when you start tacking upwind, you should learn to pull some depower, you will see the kite move more forward into the windwindow and you will be tacking upwind with ease and without too much upperleg pain.
Lightwind is an art of itself, it takes much more skills to go out in 10knts and keep it all going than with 20knts ( not with the sector and 12M then
)
try to find enough info and you will see that these boards can bring fun when you get the right techniques and tickle the last bit out of them...remeber swimming back onshore might happen too...
cheers
dude