Standalone is using the same GPU percent as the Modo plugin. So the issue is as per the top of this thread.I exported the scene in Orbex, just lunched in Stand Alone and this is the results.
Paulin order to get 100%, you need a complex scene, since with a simple scene everything is running too quickly to max out the GPU. See "overhaul of the integration kernels" in viewtopic.php?f=24&t=51679.