I realise this is an old thread but the topic is still valid today.
I would advise to set all nodes to MIN to start with and see how it goes. Then increase one step at a time until you get good communications. Don't forget interference from microwave ovens, wifi, bluetooth. That's why you should allow a few days between tries to get the best solid communication with the least power.
If you have a lot of highest power ones you are creating an electronic 'smog' that can affect other devices and possibly your health.