Quote - I do it with materials.  If I was doing a dress I'd divide into 3 mat groups Top, Skirt and Waist.  The waist mat group is like a belt between the top of the skirt and the bottom of the top (:?).  Depending on the garment I make it from make it as wide as is necessary.  But if it's a dress I usually make it one poly thick.

but wait, that really creates a weird situation.   let's say you create that waist section first.  it's only 1 poly thick.  it doesn't actually exist as a vertex group.  if you create your waist constrained group, then create the top dynamic group from the top material which holds the top set of vertices from waist, and then create the bottom dynamic group from the skirt material which holds the bottom set of vertices from waist, isn't the constrained group now empty?  or can the vertices belong to two groups?