Blrfl
Natural Rider Enhancement
Better would be to leave the plugs in, because there's no need to remove them when changing the shims. The spark plug wells are deep enough that any tool you stick in there isn't going to reach the place in the cylinder where the shim would have fallen.I'm thinking it may be a good ideal to run a magnetic pick up tool in the plug holes before finishing it up when doing a shim change.
I said to Nick in a PM that a plug hole is the most likely route in since you wouldn't have shims anywhere near the intake during a change anyway.
--Mark