I know it is a couple of days late, but I just wanted to suggest something...
Using some software such as MSI Afterburner or EVGA Precision X, you can add an offset to the maximum clockspeed without effecting voltage.
Same voltage but a higher speed means that the cooling will work fine as no extra heat is created.
I believe it goes up in steps of 13MHz, so take it up a notch at a time until the GPU crashes, then revert to the last stable one.