Richard, I'll let John Miller answer you about the size, because he and I are considering on buying from the same place and saving on transportation costs, since we live near each other. I'm afraid to keep the hay in my barn. As a neophyte, my fear is that I'll do something wrong and start a fire. If any of my animals were killed by that, I'd never get over it. I do have an old carriage house that I use for a garage with a large loft. I would use that for hay storage also. Between the carport and the loft, I should have enough space, though it would be tight. As far as the carport is concerned, I would extend the sides, so that it had walls to further protect the hay.
As always, Richard, thanks for all your advice!!
Rich