Yeah, they drape too much at default, I tried playing around with the dials but didn't get very far.. try adding all the verts to the constrained group, might work with that pose, might look terrible.

Another thing to try - in the first frame make Make Antonia and the panties like 80% y-scale, in the 15th or so frame make Antonia 100% y-scale but keep the panties 80%.. if you have the top row or two of them constrained it should compensate for the vertical drape and make them stretch to fit.  (I've done that several times fitting tight dresses to thinner than default body morphs, not tried with these but same concept should apply)