Dynamic update of stereo layers

I’m trying to use the new stereo layers component in 4.12 for my HUD, but I need to dynamically update text rather than use a static texture.

I’ve tried creating a “Canvas Render Target 2D” variable and drawing the text on it as per this tutorial:

Then I call “set texture” on the stereo layer passing in the canvas holding my text. No errors are shown, but the layer isn’t updated.
I’ve tried calling “mark texture for update” on the layer and setting it as a “live texture”.

I’ve set a break point in the C++ code and it doesn’t seem to be stepping in to the Set Texture function even though it’s executed in the Blueprint

Should what I’m attempting to do work or is stereo layers only for static textures?