For a little bit further clarification:
I called and spoke with Customer Service rep Maria at the TST Office in Cumming, Ga. (770) 889-9102. I asked her if rubber valve stems can be used with the 507 TPMS bottle cap style sensors? She said yes. She went on to say, that an application requiring flow through sensors, it would require metal valve stems. To their knowledge nothing has changed in the install instructions with regard to use of rubber stems with the bottle cap signal sender.
Safe Travels!