PhilC's Poser PocketKnife can delete the FBM and all associated PBM's in one swoop.

Which is handy, because even if you make one small PBM in V4's left shin, Poser generates a Custom Morph dial in all 50+ body parts, from the tips of her fingers to all of her tongue joints. I'm constantly using Pocketknife to delete all the extra Custom Morph dials.

The day Poser creates a new dial in only the parts actually morphed, I will be a happy camper.