I have improved this:
It does passably well enough for me rotation wise, but i don’t htink it can ever be complete without a bit of panning too.
Edit: Here’s a ‘near perfect’ way of doing it Planar reflections not working - #20 by Cestarian
It almost 1:1 matches planar reflections in accuracy, the biggest problem is that whenever you rotate the camera the mirror spazzes out a little bit, and if you want to perfectly stop rendering of objects between the scene capture 2d and the mirror you still need to use global clip plane like planar reflections does.