Just run 1100 MHz on core and 2000 Mhz on memory and you'll fine. Undervolt some like 850 mV maybe.
The most stable overclock settings for a rx470 I had here is 1200MHZ for core and 2100 for MHZ, overclocking stability depends entirely on the memory of the gpu, mine is a OC editing Micron memory, I used 850mV too