I'd go with at least a layer of damplifier on each of the doors...making sure to cover up all the holes and such. Then put at least 1 layer of spectrum on the doors as well. I would then put 2-3 layers on the rear wall and side panels.
You're prolly looking at around 40sq. ft. of damplifier and 2 gallons of spectrum...
As you can tell, yes...I would get second skin. Don't forget to use the forum member 20% discount
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NG