What are you using to create the seals around tubes passing through the 20 mL vial caps? Do you have a link to them?
I have some extra 20 mL vial caps lying around, so I drilled 5 holes into one and want to add a fifth tube to connect to fourth pump (3 media, 1 waste). Let me know if you have any suggestions on ways to drill the holes or anything else that is relevant. Thanks!