If that is #8 in this illustration...
View attachment 133732
...I would think come of the adhesive backed sound/heat insulation would work fine.
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...key to absorbing sound is mass; so a insulator that is heavy like an adhesive butyl sheet. Kilmat worked well on the Land Rover 109.
Cheers
Bill
KILMAT 80 mil (2 mm) 36 sqft (3.4 sqm) Car Sound Deadening Mat, Butyl Automotive Sound Deadener, Audio Noise Insulation and dampening : Amazon.ca: Automotive
KILMAT 80 mil (2 mm) 36 sqft (3.4 sqm) Car Sound Deadening Mat, Butyl Automotive Sound Deadener, Audio Noise Insulation and dampening : Amazon.ca: Automotive
www.amazon.ca