So I backed down to 4.3, and so far the stability test is still going after 2 minutes. Going to give it 10 minutes, crank er up to 4.6, give it 1.425v to play with, and see where she stands...
EDIT: Haven't changed anything else besides the multiplier and Vcore. Multiplier is up to 21.5, vcore is up to 1.3375v.