Expanding the battery bank

We are expanding the battery bank to three strings of batteries. The primary reason for doing this is to decrease the cycle depth. The bank typically drops to 12.6v each night. My goal is to get this closer to 12.7v to 12.75v. Two more DC335-6 batteries will bring the capacity to ~1000ah at 20C discharge rate. A 20C discharge rate is 50amps per hour for 20 hours. I figure on average our consumption is 10 to 15 amps per hour.