Hi icandy, I've just run some test simulations to see if I can help,
I remembered a discussion when bopperthijs was creating "Bopper's Spring Outfit"
which is a hybrid pleated skirt, which looks like it's exploding during simulation but renders fine.
This model has quite deep pleats modelled from the hip band and double row of verts as constrained group at the join between hip body part and dynamic skirt.

http://www.renderosity.com/mod/freestuff/details.php?item_id=49523

and Biscuits Short Dynamic Skirt

http://www.renderosity.com/mod/freestuff/details.php?item_id=69184

this one has the entire model as a soft decorated group and is also modelled double sided.

I tried the whole skirt as soft decorated with PhilC's J5 Halter dress, it seemed at add considerable weight to the skirt and there was irreparable poke on the hip straight away and complete failure on the thighs, makes me wonder if Biscuits technique actually needs the double skin to make it work.
I ran a few other tests trying alternate vertical rows of verts as soft, rigid and constrained groups all to no effect.

What seemed most significant in the two successful models was the distribution of polys, much denser rows in the folds and broader spacing on the flats. If only one could ascribe behaviours to edges in the cloth room.