Proof that some kind of progress is taking place, I just finished a false rump. Made in nearly the exact same way as a bumroll (which is an earlier version), this is a crescent-shaped pad tied around the waist and used, particularly in the last quarter of the eighteenth century to hold out the skirts in the proper shape. With the decline in favor of the pannier or pocket hoop, the false rump, cork rump, or rump pad helped to create fullness in the back, while maintaining a smoother and straighter silhouette in front.
I haven't found any documentation yet on just how cork rumps were fashioned, though one assumes that the material indicated was somehow involved. This one is made of black and red brocade that I had leftover from a previous project. It is stuffed with scraps of fabric, rags being an authentic method of doing so.
Still at work on that pair of stays, though it is hanging in the sewing room while I work on projects for friends.