I'm 110kg and I use surfboards rather than kite boarding company directionals.
I ride Aviso boards that are hollow carbon fiber replicas of surfboard shapes
(that pay royalties to the original designers).
They are great for big riders because they are light and have a very efficient
flex pattern. They are very ridgid from tip to tail in the rails, but have loads of flex along the centerline.
This absorbs chop and gives you a recoil effect in the bottom turns.
The Don Johnston 6'8" mini gun would be a great board for you.
It is a quad concave with moderate but effective rear rocker.
It is best suited to riding strapless due to the mini gun shape... narrowish tail.
You do need to move around the board and it likes to be ridden on a forward stance.
It goes upwind like crazy.http://www.avisosurf.com/DJ6-8.html
I also highly recommend scimitar fins by Future Fins.http://www.thesurfboardwarehouse.com/p- ... mitar.aspx
I have lent this board to several heavy riders and they instantly love it.
It's easy to ride, has loads of flotation, but just needs to be ridden with your weight more forward
and very far forward for the best upwind performance.
With this board I am often out with the same sized kite as people way lighter than me.
My absolute favorite is the Doc Lausch 6'1"
It is a bit more technical to ride for a heavy guy, but it is really fast and efficient.
You just have to really move your weight around well.
This board has a slightly elongated flat central section that gives it speed and low end, however it has quite a pronounced tail rocker. If you don't distribute your weight well the tail rocker will slow you down. The Scimitar fins really work on this board too. Huge difference.
Regarding the Scimitar fins they come in a set of three. Just use the two outer fins. The middle fin is a wierd shape and I don't like it at all. I just use a more standard middle fin or just no middle fin depending
on what I want to do.
Regarding the Aviso boards... they are very expensive new, but I often find them used in mint condition for really good prices. Even as low as $ 350.
Keep in mind they are not board to use for big jumps with bad landings, especially if you use straps. I cracked a couple when using them with straps. Since I have gone 100% strapless no problems at all. I also like the idea of using a board that will give in before I blow out a knee, ankle or whatever.
One time I fell on an overhead wave and my board was thrown at me and hit me right on the knee.
It pushed be against the sand under the water and caved in against my knee. I'm convinced this saved my knee and it only took about 1 hour of work to patch up the board. These boards are actually very easy to repair. They are also way more ding resistant than any other directional kiteboard or surf board.