A better fix would be 0.002 undersize bearing inserts if you can find them. They used to be fairly common.
[on edit] If you're already .010 undersize, you're out of luck. They never made 0.012 undersize. Have you miked the crank? Also, blocks can get warped a bit, possibly causing what you're seeing.
The tinfoil trick is a bit redneck.
