Here's EXACTLY what you do PUTTY!
you motor over to home depot or Lowes and buy however many rolls of the 30lb.' Felt' underlayment roofers lay down before running out an asphalt based shingle roofing system,,, my horseracing buddy and myself laid down a 5000 sq.ft.+ ranch house in that pergo fake hardwood flooring casing-liner stuff,,,it's the cheapest stuff going and its better than foam padding that deteriorates into dust over a period of time.
Yer' pal Melon knows these things,and 'likes' you enough to share