How to cut sorbothane?

Whoops, I also didn't see that you got the discs made.
In the words of Roseann Roseannadanna
'Nevermind'.

I get a kick out of some "diyers". While I understand the idea of saving a few bucks when you can, it's interesting the extent some people go to saving those few dollars. As a person that has sold industrial products my entire life I get a kick out of those that just know they can do things cheaper, better, faster..............until they try. They run around trying to find the right tool 'cause they know they can do it. But they spend more time and expense chasing after just the right thing than if they would have bought the original product in the first place. Personally, I just bought some vibra-pods that corresponded to the weight of the items I wanted to insulate, cut some manilla folder material to fit the same profile as the vibra-pod (using a standard pair of scissors) and I was done. I don't mean to chide anyone's efforts at saving a few bucks but there comes a time when it's just not worth it. Just buying the right product for the job may actually be the best answer.

Correction to my earlier post.  I recommend Durometer 70.  I don't know if you can buy it from McMaster (I bought mine directly from Sorbothane), but higher is better.  If you were able to cut the other with a punch you may be able to do it with 70, but the hardness is about double.

Someone referenced the relationship between Durometer and absorbing different frequencies, which is partly true.  All durometers absorb higher bass frequencies (50-100Hz) effectively.  Higher durometers will compress less with the same weight and have higher absorption coefficients in the 15-50Hz range.  Note that you can't compress the material more than 20% or it will internally cook and degrade over time. 

Falconquest, sometimes a better education results from trying things for yourself.
True, it would be 'easier' to have it made to order, but, sometimes building it yourself not only gives you the pleasure of accomplishment, but also greater understanding of what works and what doesn't.