By the way, a good reference for Pi to Pi nRF24L01 is the #13 Tutorial by Module143: (1) Rpi3 Tutorial 13 – Pi to Pi Python Communication with NRF24L01+ - Module 143 Sushant Narang 216jun13
http://invent.module143.com/daskal_tutorial/raspberry-pi-3-wireless-pi-to-pi-python-communication-with-nrf24l01/

(2) Rpi3 Tutorial 14 – Pi to Arduino Python Communication with NRF24L01+ - Sushant Narang Module 143 2016jun14
http://invent.module143.com/daskal_tutorial/raspberry-pi-3-wireless-pi-to-arduino-communication-with-nrf24l01/.