I built a test piston for the Holt 75. The clearance from top of piston to top edge of the bore is .201. The head button protrudes in the cylinder .030. Add a .010 thick head gasket & that leaves about .1.81 for the combustion space. The bore is 1.00 & the stroke is 1.250. How would I calculate the compression ratio? Thanks, Capt,n