Multiplayer Google Cardboard with UNet?

Hi everyone. I was hoping to make a Google Cardboard (and eventually Daydream) app multiplayer. I expected it to be fairly straightforward. Make and spawn a player prefab with everything attached. I'm only turning on the Cardboard stuff if it's the local player. This prevents the situation where there's several cameras rendering at once.

When I only have one player in the scene, the camera renders appropriately. However when I add in other players, I get the error message - "There can only be one GvrViewer object in the scene." And the player's view turns to black. (See attached.)

I'm using Unity 5.6.0b3 and the latest GoogleVR sdk.

My question is essentially this:
a. Has anyone done any multiplayer Google VR before?
b. What am I missing/forgetting to turn on/off?

Thanks!

 

I have the exact same problem too! Do you finally know how to fix it?