I'm new to overclocking, but would like to add some data to this thread.
Batch L640 (NewEgg)
Maximus IX Code (BIOS 0701)
Custom Watercooled, Open Case
Only 3 changes made in BIOS: Set to 50, LLC Level 5, and Manual Mode Voltage
5.0 @ 1.20 = Windows 10 wouldn't boot up
5.0 @ 1.23 = CineBench R15 crashed
5.0 @ 1.24 = CineBench passed with Max Temp 63c (RealTemp)
Didn't hit the lottery, but I guess it could've been worse. Any pointers will be appreciated.