Well.. I tend to take overclock claims with a grain of salt because of... differences in what the individual deems acceptable stability. For example, one person may not stress test at all. While another may decide a system it not stable until it passes 24 hours of Prime 95, 24 Hours of OCCT, *and* 3~5 passes of Linx with no errors. Even screenshots of CPU-Z/GPU-Z aren't really "proof", since the system only needs to hold together long enough to take the picture.
The second point is that - due to manufacturing tolerances being what they are - even supposedly identical components aren't necessarily equal to each other. Not to mention the quality of the motherboard, power supply, and other system components also matters.
So, while other people's settings and benchies are definitely a guideline, they are certainly not gospel. And just because Jack gets 4.2Ghz on Air at 1.2 volts, doesn't mean that Jill can.
Think of Overclocking as in Iterative process: Overclock a little, test for stability, Overclock a little more and repeat your tests, etc. So what I would do at this point is go back to stock and pick a couple points in between to stop at and check stability on your way to your target.