1080 g1 2050 core -i 27 405 mh, I think this is stable. 400 mh is stable though with -i 26. 1080 doesnt scale well with overclock. windows 8.1. -i 28 has nonce problems
I'd love to see a screenshot of the 1080 above 400.
did you remember to reduce the memclock? Use NVIDIA inspector -1000 mhz. Then you have more power to overclock the core..