Cometic offers two thicknesses as follows:
86mm bore .043" squishes to .036" or .914MM or 5,309.2600176 mm cubed or 5.309 CC
86mm bore .059" squishes to .052" or 1.32mm or 7,667.640288 mm cubed or 7.668 CC
And just for grins the Wossner 86mm piston has a dome volume of 0.23964819 CUBIC INCH or 3.927130227014 CC
Better factor that into your calculations
