Well, I wish I knew. The only references to the FBMs/PBMs are in the BODY, and the chest. I've slaved translation/rotations of the lChest and rChest groups to the BODY actor. I set it up that way, intending to use it as "fits." And I got this result.

Now, the chest references are not connected to anything not even the BODY actor FBM/PBM code.