I prefer PS, but 4 down from your natural waist sounds right for the NS (granted you're going for a fit like most people here seem to prefer). The fact that you said 'natural waist' leads me to believe that you actually understand what's going on. People use 'true waist size' to mean several different things. I would love to have some agreement about the term, but it would be a giant headache to bring about. also, Levi's lacks consistency with their actual measured waists (not sure about LVC) so I wouldn't think of it as a point of reference.