You can't assume
a max safe vCore without taking temperature into account. I would try to keep the CPU under 55C (preferably under 50C) by SmartGuardian readings. See how high your CPU temp rise according to SmartGuardian, and try up to 1.55V. It will break 50C barrier before you reach 1.55V with air-cooling and that's usually where stability problem starts showing up. With decent air-cooling, 1.50V will often be pushing it to/over 55C but every CPU, HSF, environment are different so you'll have to test it out for yourself. When overclocking, there is no such thing as max safe voltage.
