I have both RX 470's working now (4GB and 8GB) with latest Claymore's Dual miner.
Running it in ETH mode only atm, but both are mining without crashes.

8GB card is running at 24.xx Mh/s (drivers v16.8.1)
4GB card is running at 22.xx Mh/s (drivers v16.7.3)

-tried dual mode ETH+Decred:

Decred speeds:
8GB card is running at 369 Mh/s
4GB card is running at 321 Mh/s

Both Sapphire Nitro+ RX 470's at stock speeds.

Nice to see them both hash, Claymore's miner ftw!