Zpool Stratum Difficulty
By default, zpool will adjust the difficulty of your miner automatically over time until you have from 5 to 15 submits per minute. It's a good trade off between bandwidth and accuracy.
You can also set a fixed custom difficulty using the password parameter. For example, if you want to set the difficulty to 64, you would use:
You can only lower the difficulty 1/2 (half) of what the stratum server starts your initial difficulty as.