Can't seem to get a good stable OC for the death of me lol. Any suggestions?

My dual mining hashrate for ETH currently fluctuates between 42-48Mh/s from two 8Gb Strix RX 480s, with one card around 20-23Mh/s and the other 24-25Mh/s. I've read that people are able to get 30-31Mh/s from these cards through OC but outside of the default OC at 1330Mhz in GPU Tweak 2, everything crashes after a while. I had managed to get to 51Mh/s but it crashed. My rig is as follows and any help/guidance would be appreciated.

Ryzen 7 1700x
Asrock x370 Taichi Mobo
Corsair H100i v2 Liquid Cooling
(2) Asus Strix RX 480 8GB running with Crossfire - Driver 17.10.1731
32Gb Ram
750W Power Supply
1 SSD, 2 Sata HDDs
NZXT Phantom with 5 fans (1 200mm, 4 140mm)
Windows 10 64bit

Any ideas or advice on getting up to 50-60Mh/s?

Edit: It just crashed on the default OC as well.. smh