Another option you might find useful is to export the displaced mesh as a .vrmesh with the following MaxScript command:
$.modifiers[1].write_vrmesh = "C:\\PathToYourAssets\\cliff.vrmesh"
After rendering, you can disable the export by
$.modifiers[1].write_vrmesh = ""
This way, it won’t be exported again during subsequent renders.. Once the file is generated, you can load it as a VRayProxy and use it as the surface.
Best regards,