Most likely a futile, "throw enough mud at the wall" type suggestion - considering the impact of the dual card. Could Windows and Poser be offloading display and OpenGL rendering onto the 1050 leaving the 1080ti free for ray tracing only? One thought is these two functions are throttling the 1080ti. It is possible to control how CUDA is used in the Nividia control panel 3d settings so it may be possible to mimic this behaviour when using one card only.