got the head cut today, was surprised how well it went.
Had to make a fixture as the 4 jaw chuck was a self truing chuck (no independent jaw adjustment)
cut the head at 14 degrees (just slightly more than what i measured the piston at)
bore is now at 45mm with just under 50% area used as squish band in the combustion chamber.
I have to check the new volume of the combustion chamber and will take some more material out of the dome if need be to keep the C/R under 10 but otherwise shes ready to go together.
Edit: does anyone know where i can find the angle that the factory decomp valve is cut at? the seat in the head looks square cut and id like to hit it with an angle before lapping it in for a better seal (edited)