The CCC Overdrive utility is not horrible for overclocking with the stock fan, but something like MSI Afterburner gives you a bit more control and lets you push a little harder. 90C isn't horrible for an overclocked GPU but you're always best to shut it down at the point you're no longer comfortable with the temperature. E-peen isn't worth the anxiety.
Having said that, I decided to do a little messing around and renamed my executables not because I have a multi-GPU rig but just to see if any driver optimizations for other applications might give me a boost for the XIV bench, which they did not D:
And so now, I offer my final score for artificial e-peen extension and await my humiliation at the hands of you multi-GPU tyrants ;D
5746 hires; CPU @ 4.35ghz, single Radeon 5870 1.30v, 1070 core, 1290 vram