I have a 20m AERO which I use for under 10 knots with a directional board.... above for a wakeboard.
I plan on getting a 16m AERO 2 and an 8m AERO 2 and maybe even a 6m AERO 2 ( for those "windsurfing winds"
I've also got a 12m X2 as this kite soooooo kicks ass!!
I'm 75kgs.... maybe you should get a 20 for those lighter days......