How do I suppress the SteamVR compositor floor bounds?

This is in reference to creating a seated experience with Standing Mode room calibration, just as if you were porting a DK2-style experience to work on the Vive (no hand controllers etc).

Based on my experimentation, it seems like this is up to SteamVR as a separate application, and cannot be addressed by UE4, perhaps by using a VRChaperone component on the player controller.

Sometimes, the floor bounds miraculously don’t appear. I had a superstition that this had to do with checking and unchecking the “Floor bounds always on” toggle box on the Advanced settings in SteamVR, but I can’t seem to consistently get this and confirm.

I know the audience member experiencing this game isn’t going to be moving around at all, so is there an explicit command (Blueprint or C++) I can pipe in on the Unreal side to suppress visualizing the floor in the headset?

Would love to hear an answer to this too, if this is now possible.