Are you talking about the black plastic near the magnet and around the outside edge of the driver, or the clear plastic diaphragm?
Clear diaphragm - no no, don't mess with it.
Black plastic - fair game, for me so far at least. I have melted a tiny bit near the driver magnet and have had no issues. anything done to the plastic driver shell shouldn't do much harm, it's messed around with a lot during full liberation.
The black plastic, right next to the metallic circle.