See Updates for clarification on strikethrough text.

Warning : this is very beta. The plugin adds 42 atoms to the scene, which are a pain to remove by hand if things go wrong. No longer adds extra atoms. Still experimental. Keep a copy of your scene before using.

This plugin adds several hidden capsule atoms new colliders to the legs, hip and breasts of male skin based characters so that cloth and hair collide more or less correctly. The added atoms colliders get automatically removed when the plugin is removed (but not when it is disabled).

How to use :

• Add it to a Person atom
• Wait for it to create the capsule atoms and load fully
• Morph the character
• Use the "Guess Fit" button, preferably on a neutral pose, for an initial approximation
• Adjust individual colliders as needed

Where applicable you can adjust only one side and copy to the other side symmetrically.

Limitations :

• Adds a large number of atoms to the scene. They are hidden but can clutter the selection list when "Show Hidden" is enabled. They all start with "uycol_*" so they should appear near the end of the list.
• The result is not skin-perfect, it's only an approximation. The colliders do not deform as the character is animated, but they do follow the bones and handles. Extreme poses may have some peek-through.
• Areas where there are built-in colliders aren't touched. For chest and arms you should use the Collider Editor plugin by Acid Bubbles to align the existing autocolliders correctly.
• Although minimal, there is a performance hit.
• The scene should not contain any atoms that happen to match the names of the atoms this plugin adds. To be safe, there shouldn't be any atoms starting with "uycol_". This is Extremely unlikely, just in case.
• EDIT: for now, this plugin only works on a single Person. Multiple instances support planned soon.

Major thanks to @Acid Bubbles and @MacGruber for their code which helped me figure out basically everything.
PS: Please dont code shame me