When to call SetTrackingOrigin?

I have a multiplayer Oculus Rift game, and I’m having trouble with the camera location. When not running multiplayer, calling SetTrackingOrigin (Floor Level) from my Character’s BeginPlay seems to work as expected. But in multiplayer, this seems to not work at all. Neither does calling a to-client RPC from the Possessed Event to set the tracking origin.

What is the proper way in a VR Multiplayer game to make sure the camera position is computed relative to the floor?