Quote - I work almost exclusively with V4 and after conforming the dress to her, it seems I can place her in any pose and the arms and torso of the dress move just fine with her but not on her legs.

This is common, most people rig a dress with the entire skirt as the Hip.  I don't know if there is a good way to rig a skirt in Poser that includes groupings for the legs all the way down to the feet.  Generally the vendor leaves you with some posing handles to help shift the skirt around but it's difficult to get a conforming skirt to truly act like real cloth would.

For flatting the bottom when sitting, one or more magnets at the dress's hip would be the way I'd do it (probably just one).

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