Cardboard Toggle Stereo Option?

We are hoping to make a Google Cardboard app that allows the user to toggle stereo on and off, or more specifically, to use it in 2D mode with “hmd-like” tracking, and toggle it to stereo mode to put into a cardboard headset.

We have been finding it useless to use blueprint functions like Enable HMD, and Exectue Stereo Off, as they no longer seem to have any effect in game on UE4.19 (which is the version we have built the project in).

My google-fu has failed to find any current answers to this issue either. Is there any way to toggle from stereoHMD to 2D?

Many thanks for any assist!