Artifact scanning in ATITool

I was wondering what most of you guys set your artifact scanning to in ATITool? By default mine is set almost all the way to 'Lower overclock'. At this setting, my 16 pipe C3D X800 GTO craps out at around 460MHz with a Rev5 silencer at 100%. When I move the slider to just past the last 'd' of detected, my card runs all the way up to 526MHz before giving in. Thanks.