TFB: Please post a photo of what you are describing when you say:
"However this isn't about the fitment of a trim piece, I'm basically talking about a plastic plug which is crimped in, over time fatiguing and blowing out."
The Harley switch on my 40 is 10 years old. I am using DOT 5.
A few more thoughts.
https://www.fordbarn.com/forum/showt...y+brake+switch