Hi Wulfgur,
I am 70kg, and kite in both Sydney and Wollongong. I have a 10m kite (Switchblade IDS) which gets me going in 17knots with a top end of about 27knots. I am currently looking for a smaller kite about a 7m which willl get going from about 24knots to 35knots.
A 12m kite will get you going about 14-15knots, and probably get you a top end of 24-25knots.
A 9m kite, probably good at 20 knots to about 30knots.
I am not sure of the LF Session kites, as I haven't ridden one.
Goodluck
KR