Piston rings and cylinder walls wear together. They 'mate' to each other to form a good seal that helps compression and therefore power. Once the rings have been seated to a wall, even if they are not old and worn out, they will never seal to a new cylinder wall as well as new rings will.
Most certainly it has been done and with success, but it isn't the right or best way to do it. Rings are cheap and you won't regret going with a matched set, cylinder and rings, down the road.
Treat the engine like a new one and do your break in according to your feelings. If you research 'break in' here you'll read many theories on 'the best way'. I subscribe to the run it like you plan to ride it but don't abuse the engine either during the first couple of gallons. Abusing an engine even after break in isn't smart, no matter what.
Tom
