Yeah, the added Scatter Scale is for fine-tuning SSS according to the model.  I would say anything between 0.01 to 0.02 with the existing ScatterRadius should be fine.  However, If you use smaller radius values then you would need to increase the Scatter Scale value to compensate, otherwise, you will not see any SSS effects.  By the same token, the larger and denser mesh the model is, the higher the Scatter Scale should be to compensate.