Ah, you mean ObiRigidbody! 
Okay, I have applied one now (actually it did it automatically when I added a collider to the head, like you said it would). I also tried increasing World Velocity Scale a little and setting Update Normals to Skin. It seems to be a little bit improved, but it could be my imagination - it still does jiggle around when using IK.
You should be able to recreate it quite easily; Just get a character with hair (make a test one quickly with Fuse or something like that), then apply Full Body Biped IK & Grounder FBBIK components to this character, and setup Obi Cloth on the hair mesh like normal (but in Late Update sim order). Now try and walk on some stairs for a while, or very uneven terrain. Of course make sure the stairs (or whatever) are on a layer included in the Grounder Solver. If you find a reliable solution I'd be glad to hear about it.
Cheers
Okay, I have applied one now (actually it did it automatically when I added a collider to the head, like you said it would). I also tried increasing World Velocity Scale a little and setting Update Normals to Skin. It seems to be a little bit improved, but it could be my imagination - it still does jiggle around when using IK.You should be able to recreate it quite easily; Just get a character with hair (make a test one quickly with Fuse or something like that), then apply Full Body Biped IK & Grounder FBBIK components to this character, and setup Obi Cloth on the hair mesh like normal (but in Late Update sim order). Now try and walk on some stairs for a while, or very uneven terrain. Of course make sure the stairs (or whatever) are on a layer included in the Grounder Solver. If you find a reliable solution I'd be glad to hear about it.
Cheers