generally speaking:

a certain size kite in a certain size wind will enable you to kitesurf(lots of other factors, direction, board size etc).

i have found that i "CAN" use a really small kite in small winds, but the reduced area of the kite don't work as well. Less hang time, more jerky pull blah blah and other stuff i no nothing about. It just feels wrong.

I just think that a certain size kite pulling a certain size weight has a comfortable bottom end and if an individual of 75kgs tries to use a 7m kite in really high winds then the kite displays a skittish behaviour. The 7m is pretty much at a bottom end, if oyu completely depower a 7m i reckon you could go out in 40+knots(and according to some of my previous exaggerated posts you couuld do that monday thru monday here in perth :)

Don't get me wrong. You will be ABLE to use the kite, but i have found its not much fun. Better off buying a slightly bigger kite and then your burd(who will be kiting in light winds anyway) will be able to depower the 9m and you will also be able to use the 9m in heavier winds when the burd is on the beach crying and ironing and keeping your towel warm and (any other stupid cave man chavunistic comments I can think of)