I think it would come down to a micrometer, too. The first thing that happens, when I take my cylinder in, is they mic the whole cylinder. Also the piston measurement is so many thousands of clearance to the cylinder, and that measurement is different for steel sleeve, than from nikasil. Tighter tolerances with stock.
If I know there is not much time on a cylinder, I also visually inspect for wear. It's still sketchy, on what new rings will do to the cylinder, though, but I say "Slap it in there" If it wears out after this season, you still got your money's worth, and you plan on getting a new cylinder anyway. you can always buy an extra base gasket and check piston and cylinder after break-in and redo cross-hatching, if you get a smooth area going.
how did the piston and rings look?