But obviously some JCMs should go into the figure around the arms and hips/leg area because that will be where the majority of your issues will lie.

Pollution!!!! :) I think why people stay away from jcm's in Poser is because they do not copy across in clothing unless they are unhidden (I could be mistaken), and to look for all jcm's on a figure can be a mission. In Studio, anything that has a value, be it hidden or not, gets dynamically transferred via auto-fit, hense why jcm's are more commonly used, because it doesn't affect clothing since they are on the clothing as well.

My Renderosity Store