rig set up is a hard, im starting to move my rig around at the moment, at 90 kg try and have it more forward as you can can handle the power.
what i have done, when i got a new boat, i set the rig up nearly straight, i went out and the steering was too light as in the rudders had a mind of its own, so i dropped it back, then try it out, i kept on raking the mast till i got weather helm, so you have a series of chain plate holes you can play with, in my case i have 5 holes to adjust the rake. but i put in the middle as a happy medium. thats a starting point. as for me as the weather gets heavy i rake my mast back only one hole as i just start to get weather helm, so the bows don't dig in and and less power in the sail, wind range 17 to 30 knots. in light and choppy conditions i put rig one hole forward from happy medium as it drives the boat forward into the waves and get max power, but all normal days the happy medium,
diamonds play a big part too, 90kg from want tension at around 27 on the tension gauge.
this is my view on the mast rake, others may be different.