I come out at 98cc with your bore and stroke - but that's not really the issue here.

Most model IC engines seem to use aluminium for quite a lot of parts - but yours is rather larger. Perhaps you could think about cast iron for the cylinders, and for the piston rings, with aluminium pistons.

You've discussed the sealing requirements of the rings - but you also have the gland to consider where your piston rod goes through.