My recommendation is to set the parameters as follows:
Fan Control Mode: Custom
Minimum Duty Cycle (%) 40
Primary Temperature Sensor Processor
Minimum Temperature (°C) 63
Duty Cycle Increment (%/°C) 3
This ensures that the fan smoothly rises over a 20°C temperature range from a slightly more-conservative 40% minimum and reaches 100% at my recommended 83°C Tcontrol setting.
Now, with these settings in place, if the fan is spending a lot of time up near its maximum speed (~6000RPM), it is a good indicator that the heat pipe unit is not going its job - which is usually the result of a (shall we say) less than optimal connection to the CPU and PCH...
Hope this helps,
...S