Well if you do a search you'll find this topic has be covered 100000000000000000000000000000000000000000000000000000000000000000 times.
Fatmat is the same as Dynamat but half the price. You need to create multiple layers to have any real benefit like so
Dyna/Fatmat on all panels
Mixture of between 3/6/10mm CLOSED CELL foam using high temp adhesive
Rubber matting