Like Brickguy, I've been doing the shim bit for years now; I use the largest size my fingers can fit into. Then when they shrink I insert shims until it just alows my fingers to fit.
This solves another problem I have. I will often insert my fingers without thinking about it; if the inserts are too large, my fingers goes in below the first joint. In drier weather, like the winter here in the Northeast, especially when I use the rosin bag too much, my finger will dry enough for the skin to crack below the callus. When blood seeps from the cut into the insert, the ball is harder to hold onto ... So if I can only insert up to the first joint, it won't crack.
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"Just because you can do something does not mean you should do it."