Last season we expanded our birch operation to around 700 trees. We hung clear plastic bags. We hauled about 8000 gallons to make about 65 gallons of birch syrup. Our last batch turned out close to the same as the first batch, a nice red color. I wish we could run a big RO but we are off grid in northern Minnesota. We use a 3 post 4"x40" homemade RO. We were able to get the concentrate to an average 7% sugar. We use a Murphys cup to get to 67-70 brix.