Slow, flexible and cheap: Six years of development to create a rubber hexagon
> Turns out, a slit really isn’t the best shape for the hole because if you don’t have the right kind of rubber, it can rip too easily. A circle is better because there’s equal pressure around the hole and it’s less likely to rip. I wish I had considered this sooner, but that’s what it takes to learn and that’s why I’m sharing this here.Given the level of detail in the article, I'm led to believe that the next moment hasn't happened yet..What you really want is a slit with a pair of small circular  holes, one on each end of the slit.  o--------------o

All the benefits of the slit without the tiny points where all of the stress is focused, which is what causes the ripping. Adjust the size of the holes as needed.Common design trick for sheet materials, and should be straightforward to cut with the same machinery.Enjoyed the article.