If those are your pistons pictured, with no reliefs out to the edge, there is no need to cc them in the cylinder. You can just use a plate with a hole in it, seal it to the top of the piston with some grease, and cc the dish just as you would a cyl head chamber.
The cc-ing of a cylinder is usually used to find cc of a domed piston, or one with a dish that has valve reliefs to the edge that cant be sealed with a plate.
Now, that will get you dish volume, but that is only a SMALL part of determining actual compression ratio!
