>>16719
You could probably rig it using the fitted mesh BUTT collision volume, since that responds to physics settings and is a child of the mPelvis bone. BELLY might also work, but I don't remember if it's directly attached to mPelvis or something else. This would, of course, require you to be careful with those sliders, since they'd affect its size.
It's kind of surprising that nobody's used BELLY rigging on a fat mesh body, come to think of it.