K5 bed floor level under carpet

[Vetteman61]

I'm installing aftermarket rubber interior floor mat throughout my k5. What have you guys installed underneath to level out the floor so the rubber lays flat?

 

[Chevy 88]

I'm installing aftermarket rubber interior floor mat throughout my k5. What have you guys installed underneath to level out the floor so the rubber lays flat?

Padding would "reduce" the number of imperfections in the appearance of the rubber floor lining. It would also reduce noise in the cabin.

 

[Zelph]

I assume that you are talking about the cargo area?
Cut some butyl noise dampener into strips that will lay into the valleys.