Utilizing Full Reality Mesh as Base Terrain in ConceptStation

Is there a way to incorporate a full Reality Mesh created from drone imagery as the base terrain for a model in ConceptStation? I have flown a project site and gnereated a reality mesh that I was intending to use as the backdrop/existing ground for modeling a proposed railroad grade separation project for a client. I can attach the reality mesh in ConceptStation, but the templates will not target it as ground, nor will it clip it properly. I have to create a terrain extracted from the reality mesh in ConceptStation, but this flattens my data and does not look the way I want it to look, and the extracted ground does not look the way it should either. How do I go about generating a full 3D model that includes both my proposed design and my full reality mesh?