skin tone saturation on vectorscope?

Ok here goes another question I've had for a long time and never seen addressed. Everyone says that flesh tones should align on the skin tone indicator line on the vectorscope. but what about how saturated a typical skin should be? Assume your vectorsope is set for 2X's , are there limits you should watch for. I realize every one's skin is different and every shot is also, but there must be some general rules about how far that indicator should go. Is halfway generally too saturated? 1/3?