Each actor can only be affected by a single planar reflection, and I believe it takes the closest planar reflection based on centroid of bounding box? Or it could be based on the pivot. You might have to play with the pivot/bounding box of the meshes, and use 2 separate planar reflections. Planar reflections can be scaled like any other actor.
Thus far I haven’t found a way to choose which planar reflection should be used for a specific actor.