If it only has the one group I would make a new animated constraint and set all the vertexes to a value of .0001 or maybe 2 and constrain that to the hip.  With a value that low and setting the dial to a low value under .020 that should stop the cloth from stretching to the floor as you can see on the left side picture just above this.  Also being that low should not interfere with the normal movements in the rest of the pants.  And it should help the poke through.  But first try to get the stretching stopped.

 

Poser 5, 6, 7, 8, Poser Pro 9 (2012), 10 (2014), 11, 12, 13, 14