Custom shadow geometry for procedural mesh

How do I specify different geometry for shadow casting vs. rendering?

I’m using a modified version of the ProceduralMeshComponent from A new, community-hosted Unreal Engine Wiki - Announcements - Unreal Engine Forums to generate my meshes on the fly. I would like to specify different geometry for the visible and shadow-casting components. The procedural mesh class overrides GetDynamicMeshElements(), where I assume I have to do something different, but I’m not sure what. I see FStaticMeshSceneProxy has GetShadowMeshElement and seems to be doing this, but the logic is not clear to me.