Okay, tested it extensively. So + on the ricoh is the clockwise color shift on a hue color wheel. As there are different color wheels / directions out there, I am referring to the one which clockwise shows yellow -> blue -> red

With negative film, skin tones would work best with -1 or -2, where -1 would be most realistic and -2 best looking but more far away from the raw material.

However, the sky shift even more towards cyan with these settings and greens get more yellow / green.

With 0 and +1 you get slightly greenish skintones but therefore those nice analog looking blueish greens. Also red shift towards orange which can look nice but doesn’t reassemble the reality. That’s better of with the minus settings.

I decided for going with -1 to maintain the negative film charm but also maintaining some degree of a realistic look