Do it using an LOC , tapping from the rear speakers.
So I did some sound deadening with dynamat, put some on the rear deck on the metal, and below the plastic on the rear deck, and it made it soo much nicer now. The metal rear deck does not vibrate anymore.
Still some rattles here and there, will perfect it soon. If you crank up the volume, the music overwhelms the rattles
Heard of people stuffing tissue paper, will use foam in such places.
Im sick of spending time in my garage now. My neighbours think im nuts.