I often find myself wanting to adjust overshoots depending on specific letters. For example, the S in a serifed typeface often needs less overshoot than the O, because the S is kind of flat-ish at both ends. I know the standard advice is to have one overshoot size for caps, one for lowercase, and then sometimes another for pointy characters like V. But I'm not sure if I want to follow that advice.
Is there any reason not to adjust the overshoot per letter? Am I being overly perfectionistic? How do you go about this?