Now I am trying to push the limits even further. Overclocking often needs better cooling and increasing the operation voltage. The coldest temperature I can easily get to in my house is the freezer with -16 °C. Sticking the circuit in there and doing the voltage sweep again brought some improvement to 9.98 MHz at 5V and fine-tuned to 5.3 V got me to 10.01 MHz; above the desired 10 MHz margin twice the specified value in the datasheet.