It is good that you don't seem to have a heat problem, but .5V out of spec on a 1.7V part is where I draw the line. That is 30%. You probably can go a little higher, but the tolerances on that stuff are so small, I would start to worry about the voltage jumping the super small gaps of the die. Up to you. 30% is pretty far out of spec.
"Water-Cooled CPU Runner"