I run Klotz supertechniplate 40:1., depends on what oil you run. General rule is always safe w/32:1. I have never personally run a shaved head, always a cool head, so I am not sure what the volume of your domes would end up at, there for can't calculate a compression ratio. I am sure someone will chime in that has. I belive shaving it 30 you will still be able to run premium pump fuel. Another thing to keep in mind is if you don't have your crank welded, more compression could cause disaster.