We tried that and it didn't work because the poly wore through right where the metal one wore through. A machine shop made us a new steel one for less than half of a CaseIh one.
as a parts person for a case ih dealer i would not recommend putting the poly on over your old pan for the reason the guy mentioned above. but i a combine owner (1640) i would put it in when you get new pan. it greatly reduces the noise from feeder house. hoope this helps.