cbulota said..
For a guy your weight:
-Average board size: 134-138cm
-Big board size (light winds) 140cm +
-Small board sizes: 132cm or less
A lot of beginners are told bigger is better because big boards plane easier and you need less power from the kite and less technique to get going. However big boards are less maneuverable and can be harder to learn freestyle tricks on. They can also be harder to learn to ride upwind on (especially if they are very wide, i.e. more than 42cm wide) and generally speaking won't perform as well in strong winds and very choppy conditions.
Smaller boards are great for very strong winds, they hold a stronger edge with less effort and cut through the chop a lot easier, but that's also subject to personal preference.
Your average wind range in your area and the type of water (flat, chop, waves) and your style of riding plays a role in the board size as well.
The fact you learned in 15-20 knots with a 128cm board at 80kg is impressive and definitely shows you have a very good technique. That board is worth keeping if you like it, for strong winds.
Try borrowing boards from friends in sizes around 134-138cm and see the difference. I would avoid going over 140cm unless you wanted a dedicated light wind board.
Christian
Thanks for the help guys i will have a look around.
how good do you need to be to use a board with boots? a guy down the beach was raving about them the other day.
do boots affect the board size choice?