Taper wear in a cylinder is not linear- - - -most of it happens at the top, in the first 1-2 inches of piston travel. At 2000 RPM, a ring is expanding and contracting 60 times a second, trying to stay in contact with the cylinder wall. That makes for very short ring life if the taper wear is more than .005". Boring a worn cylinder eliminates the taper and takes a lot of stress off the rings. Out-of-round isn't nearly as critical as taper, but neither one is a good thing.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!