We have five detailed step-by-step chapters on how to tune a masthead rig, starting here, but we don’t cover fractional rigs because they are unusual in the offshore cruising world.
But if you do have a fractional rig, like we do on our new-to-us J/109, there’s a good tuning article over at Practical Boat Owner.
I agree with most of it, although they do skip over the vital step of getting mast heel position and mast blocking right, but you can fill that in from our masthead tuning chapters.
I have the same rig which I replaced when it was 15 years old. My local rigger is very old school and I realised the shrouds were too slack. I found a good rigger further away who tightened everything up and let me mark the line through the tackle for tightening up the back stay. He took 2 readings so I have a mark for max tension and min tension at all other times of light wind etc. That’s proved useful when using a big gennaker in lighter wind conditions.