storing small square bales in haymow

live in south western pennsylvannia   different people tell us different things about what is the best way to stack the hay.   We have a lean tew part of our arena and the lean tew is connected   We have double pallets and then osb plywood on top of that   and on top of that we have house wrap plastic that you wrap a house in when you build it.    is that sufficent to keep the moisture out of the hay   A friend told us that I should have put the plastic down first and then every thing else I did.   we have come across a couple of moldy bales so far that were stored on the bottom row.   Any advice would be helpful

storing small square bales in haymow