I tried two things: copy the .pp2 to a .pz2 and remove everything except for the "vertGroup" data, and remove just the object geometry and leave everything else in. I'm not used to mucking about with pose files anymore, though, so there may be something obvious I may have missed. If anyone knows how to make it work, it would be great if you could share an example file, so I don't have to strain my reading comprehension. :grin:

In this specific case, it turns out that if I load the dress with the "sleeves" pulled closer together, constraining them just at the top of the shoulders works nicely for pretty much all poses except when she's straight up lying on her back.

-- I'm not mad at you, just Westphalian.