I am rebuilding a D60 Power-loc and I have been told you can shim them to stiffen up the slip.
I did a search and found only a suggestion to add another clutch disk, but that won't fit in the case half's
I am just looking for someone who has installed shims and how much? Did you like the end result or would you add more?
I can try Trial and error, but I would rather have a number.

B

I 2nd this

We flipped the discs and added one. Nice and tight now.

Never used new parts for a power-loc, we just flip and add. Also works on a trac-loc.