Joop - It depends on the spot/winds and board you ride mostly - I have 84 kg and either have 10-20 knts or 20-30 knts : 14 and 10 are perfect for me to max out the lower and higher wind range -
If you have a chance try the kites first -
It also depends on your style. If you are wake styler, take the 7.
If you are normal rider and like to jump, take the 9.
It has a big depower, so 30+ should be fine with 80 kg.
And if in doubt, I bet you will use the 9 more than a 7 for sure.
I used to have an 8 sqm C kite years ago...used it twice a year...now I save the money and skip those strong wind days, since they are gusty and dangerous anyway.
If you have daily 34 knots, then it is different...
IÃƒâ€šÃ‚Â´ve just 2 kg less and can tell you that a Rebel 7m was HUGE fun in wavey conditions from 25 kts upwards. For 34 kts other than flat water old school riding 7m is a must. I already changed to 12m Rebel when I was too lazy to rig earlier (10m) and the 7m easily works with some wave support down to 20kts. As the 7m Rebel starts to enter its sweetspot round 25 kts you needed to ride the 12m up to that point, which I found pretty much o.k. in flat water, but definitely not in waves. I guess you missed some fun zone in the 22 - 25 kts range. So if you got either winds round 12-20 kts and strong winds 25+ thereafter, this quiver works. If I think about Brazil youÃƒâ€šÃ‚Â´d be out of a 12m sweetspot 90% of the time as 9 or 10m are pretty much standard for your weight in those winds. From my view a 9 or 10m size is an absolute must for anybody kitesurfing wolrdwide.