yup, it takes time and effort Andy, I don't think anyone said it was easy
the best way is using a digital angle gauge as that just gives you the head angle set with you on the bike. TBH once sag is set the difference 5 or 10mm ride height at either end isn't great and could be taken up on preload adjustors, not exactly a big job.
Or you could just ride it, mate of mine was out on RTL, bog standard 999R no shock mods, forks set as they left factory and I doubt if anyone was anywhere near him for corner speed, talent usually compensates for set-up, the bikes aren't that far off as they leave the factory.