318 rebuild Bonehead mistakes/misses and questions

After 15 years in the business, I like your "just right" answer. There is a certain feel to the cylinder walls fresh from the hone. But trying to convey that over this forum is hard. It is rougher than glass but smother than 600 grit sand paper. Experience is the best teacher. Pull that one piston and clean it and the cylinder with a good degreaser and a "Clean" paper shop towel. Then relube and reassemble. Crocus cloth is much finer and you would not be having this conversation after using it. Like emery paper but much finer.
Even crocus paper contains silicone carbide, it's just a many times finer grit. As long as you keep the fillings out of the piston and rings you're OK>