Yes, know all about PTFE and silicone hazards. I have a spray booth and masks that I use for another hobby.
As for old vs new string beds I had read that even silicone must be reapplied with use. And while slippery I don't believe it will stop the 4G crosses from denting which is a completely different issue. So it needs to work whether the 4G is fresh or dented.
2x BLX 6.1 Pro Staff 95: 12 oz., 8 pts. HL, SW 325
VS Touch Black/Focus Hex 1.23 @ 58/54