@calembendell When we started needing this solution last year, we used a similar approach as your solution. But because we needed to show both left and right eye in the spectator view, we could not use it anymore, since the TexturePlusMirror only show one eye. We also couldn’t find a good solution to use the mouse, so we had to find another solution.
The approach we use in the plugin allows us to show the Spectator screen in any mode you choose and you can simple use UMG in our Spectator Control Window. Another benefit is that we do not add any extra tick events or render targets that use processor time. The experience we have with our medical research VR game is that it keeps running at 90 fps with the extra screen. I do think however, this solution is best used in a set specification of more high end VR hardware and not so much meant for consumer VR games.