Originally Posted by NeoFauve
Bad idea. Bad, bad idea. There's a lot of tourque on those inserts, they need to be solid. How much smaller are they? If they're not too small, you may be able to use some wood shims to fill the holes, but glue them in place and tap the insert in while the glue is wet. Just like the toothpick trick, only bigger. Line the circumference of the hole with the wood.
It almost sounds like doweling and drilling is the only way to fix it correctly.
Big difference between this and a neck shim. There's no tourque on the pick when it's laying in between two pieces of wood screwed together.