If this setting was stable then 1.4 will add a fair bit more head room.
Try decreasing the miltiplier by x1 and move the voltage to 1.4v
Now run the test again and check temps.
If temps are ok the increase the multiplier again
Alright I bumped it up to x18 (3.6) with 1.3625V and the core temp is balancing out at about 50C, would that qualify as stable?