I also sent this question to Lens Studio Support some time ago (Id #226288936) but unfortunately never got an answer.
However, I would like to apply the blendshapes not only to the face area but also to the skull area.
As can be seen above the Head Mesh unfortunately has a problem (distortion) in the mouth area (the Face Mesh does not have this problem).
Maybe you can tell me how to prevent the distortion and get an even mesh in the mouth area.
As external meshes I used the downloads from: