I have read to be careful to not apply FF on any rubber, but I have also read it can cause the frame paint/coating to blister. I don't want to apply it if it causes the frame coating to soften up.
I think it is fine considering they are advertising it for such applications. Also is should not be sprayed on non-oil resistant rubber. Not just any rubber. See more below. Several forum members swear by the product. I would be more concerned with the affect of road salt than that of fluid film.
https://www.fluid-film.com/automotive-applications/
Roger that, thanks. After some more research, the removal of the factory undercoating appears to be a GMC/Chevy thing....
Haha JD power's highest initial quality award winner. Sorry, I had to.
https://www.youtube.com/watch?v=zSBsq6HBBzw
https://www.youtube.com/watch?v=bgmyl-T9fUs