My entire trunk, trunk lid, and rear deck are dynamatted and it sounds great with no rattle from the outside at all, however, recently there has been some noise coming from where the rear deck hits the back window...this happened earlier in the year (before my dynamat) and I hid a rag between the two which fixed the problem but it disappeared till now once i got the rear deck done...I am not putting a rag back in and I was wondering if you have any ideas about how to fix that problem or what to put in the space between (if you hold the tip of rear deck down with your fingers the noise stops completely) Any advice or opinions would be greatly appreciated.

 

egg crate foam.

 

Lots of people use egg crate foam or matress pads.
Like this.