man you're getting into some high voltage there. I see you notice that there's quite a jump even going from 4.5-5.. Hitting above 5.3 for me was impossible, I did a suicide run at 1.65 and wasn't overheating, was getting into the 60's in the bios (28F ambient temps) but wouldn't get past the windows screen at 5.4
I think above 5ghz it's all about getting the most out of your ram timings for those extra fractions of seconds. Nice time though!