Keeping a world space canvas at constant size during VR Zoom

So ive been pulling my hair out over this problem for a few days now and couldnt find anything on the forums or google.
Im making a VR game for google cardboard and im manipulating the cameras FOV to achieve a zoom effect. I also have a very simple non interactive UI which i wanted to appear overlayed on the screen like a regular game's screenspace overlay UI. However, the unity docs say that screenspace overlay isnt supported in VR and to use a scaled worldspace canvas childed to the VR...

Keeping a world space canvas at constant size during VR Zoom