I am getting ready to install swiftlock laminate floors. the underlayment is already attached but I have been advised to use a moisture barrier due to the house having a moderately moist condition. Swiftlock recommends a 6 mil plastic. It is difficult to work with and a professional installer has told me that I can use roofing felt instead. Do you Pros out there agree or should I stick with the plastic. Warranty is not an issue to me but a job well done is.