Just to add to what Toby is saying
I'm 80k and use 16m-19m 85% of the time. I would use the 19m all of the time if I could. Tobys getting fat at 90kg +
It's a combo you need.
First:
You need a good seat harness this is key. When things get really pumping the seat harness allows you to maintain a lower center of gravity. The waist harness when really powered with a big kite will get pulled up and raise your center of gravity thus you just get pulled of the board by the power. The seat will stay lower allowing you to really lay back and use your full weight potential to hold the power until needed.
Small Board (I have the same as Toby (FS 128).
This board does to things, first it small and great to throw around. Its also not the lightest board for it size. This is great as the board does not get blown away by the wind as you do your tricks. Second the small board really helps to hold the power of the kite (it's carves really hard if and when needed)
It's really the perfect board for Air style (I have tried a ton and nothing comes close)
Big Kite.....
Simple, Jump high, Max hang time and Slow.
I have a 19m on a 52 bar instead of a 55 just to slow it down even more.
Get a Micro loop.... Gods gift to Air Style
cheers
T