From what I've been reading, monitor overclocking via custom resolutions in NV Control Panel hasn't been working in the last few nvidia drivers. The last known working driver is 358.50. It seems they made some tweaks to GSNYC after this version which in turn caused the problem.

I can confirm this only on my setup. My Crossover 2795 overclocks just fine at 110hz, Windows 10 64-bit on the older driver (358.50). Any driver after that causes a "Test Failed" error when trying to enable custom resolutions via NV Control panel.

Anyway we can look into this further?