Bed Rail Prep for Install

Getting ready for my install next weekend and came across something I want to get resolved prior so hoping someone has some insight. I have a 2002 Tundra and it has plastic covers that run the length of the bed rail. (See pics below) Will the GFC install on top of these covers or sit down on the metal of the bed? I can work with it either way, but it it sits on top of the plastic I plan to install a thin rubber coating under it to prevent squeaking and any additional paint loss from the plastic rubbing as was caused by my last bed cap. Anyone have any thoughts? Thanks!

They will install on top of the plastic.

The Install is on top of the plastic as Jedgar states I get no noise from it.

Thanks guys, appreciate the reply