When you are shaving your head just make sure you have some thin feeler gauges around to check if you have gotten wobbly, if you can shove a .002 gauge under one sealing edge it is time to start thinking of changing strategy because you are making a bit of a wobble head.
If you have a flat top piston that levels up to the top of the cylinder then figuring as you go is as easy as using a syringe of oil and measuring the volume of the head as you shave. Keep in mind that there needs to be squish _area_ so as you shave away the gasket surface you mak have to stop because the squish band is becoming too broad. You can remachine some off to recreate the band but then you would be working backwards as far as compression raising.