I'm not sure you're going to find a shim that thin.
We're using a Thompson 28.6mm, with a shim on our Robusta. I believe the opening on the Robusta frame is 29.4, and I had to shave down the shim with a dremel tool to keep it from being overly tight.
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You could fall off a cliff and die.
You could get lost and die.
You could hit a tree and die.
OR YOU COULD STAY HOME AND FALL OFF THE COUCH AND DIE.