I bought a rear seat delete years ago and have always been bothered with the gaps under the bottom planks. I did notice an increase in road noise and interior exhaust drone. That being said I finally found some stuff that will help make it a little more quiet. It's a denim insulation similar to the stuff scattered throughout our cars from the factory. I bought a pack of six rolls through Home Depot online for $36. I thought I would make a thread and share. I think I will fill the empty void where the spare tire was.