Sid: Is your hay mostly grass??? If it is then it will shed the water better than mixed hay.
I used to use twine because I thought I could not justify a mesh wrap baler. My first crop hay would have a lot of spoilage. One year I had my baler go down right in the middle of first crop hay. I rented a mesh wrap baler to finish first crop with. I was amazed at the difference in the spoilage between the two.
My first crop hay is usually 50% alfalfa 50% grass. Then the next cuttings are more alfalfa as it will out grow the grass.