Not many adults these days with the norm of takeaways under 70kg

My advice to lightweights - try to put every ounce of your body weight thru the harness.
I use quite short lines 24inches with a very high boom - this helps me to power up the harness.
Use a surf seat harness with a very high sliding hook. High hooks reduce the lift of the board. Sliding hooks help you to put more upper body weight to the front of the board in the gusts.
And lastly,experiment with many different fins,as well as smaller sized fins.
The Techtronic Falcon is my favourite in really strong winds.
Best fin ever for putting the hammer down in the gusts.