I set my heads up with the springs, retainers and keepers that will go on that valve one at a time. I have a older Rimac 1000 lb. valve spring tester that I use to set the springs up on,I do not set them all up to the same specs.
I have hardened valve springs shims in .015, .030 and .060, I also measure all of them as I use them. I see around .004 t0 .006 variance in the shim thickness
I use lightweight checking springs to check the piston to valve clearances, intake lobe timing as well as the lift at the retainers to verify the rocker arm ratio at the retainers. I see from .015 to .020 loss of lift with the race springs on the heads compared to the checking springs
That ends up making them have from .070 to around .090 clearances on the springs from coil bind, I do that with the thought that the aluminum heads will get from .003 to .012 taller when warmed up racing it than the length of the steel valve stem will grow when hot
Lots of variables out there for Murphy to use to mess with us racers and engine builders