After releasing Zara I thought there was no possible way to improve my breast physics and rig, but I somehow did it again. From 16 bones per breast down to just five with no loss in functionality. I even improved some things while I was at it.

Testing the thigh and butt jiggle rig for my latest avatar project

I was able to remove two bones, reducing the count to 16 bones per breast. Any lower and I wouldn't have proper squish and stretch where I want it. It's still two bones more than my old rig, but it needs no blendshapes for volume preservation, meaning outfits are more optimized.

Peak physics achieved?

Empty weight "recoil bones" don't do anything. If it's the last bone in the chain, and it has no weight, it affects nothing. You're just wasting bones in your armature.