generate LightMap UVs while skipping elements with RemoveSurfaceMaterial ?

I’m trying to optimize a workflow for ArchViz. I could skip quite some work if Unreal could generate the Lightmap UVs while skipping elements flagged with a designated material, for instance sub-elements marked with RemoveSurfaceMaterial

Example: imagine a wall and I only need the inside faces in Unreal. Those faces are assigned a *Stucco material *in the 3d model software. The faces that I don’t need to be visible I assign another *Skip material *. If I have Unreal generate the Lightmap UVs, it still assigns uv space for those hidden elements.
Right now I manually assign a small space in the lightmap for those hidden faces (in the image, the red box are those hidden elements).
I prefer not to delete those faces in the 3d model software to keep the Boolean objects intact. If Unreal could skip those faces and still generate lightmap UVs for the rest I could skip making Lightmap UVs for quite a lot of objects and only do them manually for the really ‘important’ ones.

I hope it makes sense and someone has a solution.