Sound deadening rear of cab

2019 crew cab sr5 with full roll down rear window. For anyone who has installed sound deadening on the rear crew cab wall with full function back window, the black plastic/fiber curtain that was hanging. Did you reinstall that curtain? Would it hurt to not reinstall that curtain?
I have installed sounding on the inner skin where the glass comes down as well as the black panel that you can pull off.

 

The back wall fabric will help with more sound deadening

 

Thank u. Wasn’t sure if I could skip that step. But I’ll put it back. Thanks again.