J. Clarke writes:
On Wed, 28 Nov 2018 17:36:09 -0800, pyotr filipivich
wrote:

So, is shimming the collet in some manner a "good" idea? Let me
rephrase that, it seems "a good idea" , but is it a smart one?

Before you shim, clean. Get the inside of that collet spotless--a .25
caliber pistol cleaning kit is your best bet. Use the solvent in the
kit and follow up with lacquer thinner.

Yeah, I'm going go buy a pistol cleaning kit to clean my
router collet. Give me a break.

Just get a can of solvent at Ace and use a toothbrush.