Floor sound deadening

Hi, I’ve started, finally, the sound deadening process and finished the back wall today!! I notice quite a difference.
I’m starting on the floor next & just doing the back seat (LOL!) of my access cab for now. My question is whether I need to remove the factory underlay before adding MLV & foam? I’m doing the 3 stage process - Dynamat & Second Skin MLV w/foam so I think I do.
I’ve read some other threads and it wasn’t clear to me if others removed it or not. I figured it was easier to to ask first although it’s very unmanly, to ask first
Thanks in advance for any help.
Cheers

 

Take it down to metal if you're going to make the effort. I only did the inner doors and back cab wall and that was plenty imo.

 

Thanks.

 

As a counterpoint, when I did mine I left the factory head start. I didn't see what it could hurt and figured the more mass the merrier.

Could be unrelated but the floor is the quietest part of the cab, lol

 

Thanks. I’ve decided to leave the floor as it is. Back wall is done & quite a bit quieter. I think I’ll do a bit more door work and see what happens.

 

The doors are the most important part to do! I'm obsessed with the difference! I did dynamat and liner myself, just make sure you're liner is thin enough. As in ⅛", ¼" is too thick is some place on the door, but I made it work myself.