I would mock up one or two pistons, rods and crankshaft at TDC,one on each side, and seal the piston tops to the cylinder wall( I use a small tip on my handheld grease gun) and then pour it to find out exactly the volume in each cylinders is to be able to figure out exactly what the compression ratio will be
I use that method on Hemiroid motors, I'll move the piston down (I use a dial indicator to get the down travel) so the dome is below the deck by .030 or .050 and then use my plastic CC plate to fill the bore up, I'll use the math for a flat top piston down the same amount in the cylinder and subtract the measure amount to get the dome volume
Big C.I. motors are a lot easier to get to much compression, unlike little C.I. motors that need big domes to get decent racing compression ratios