Change/Override Camera IPD/onterocular

It doesn't modify the scene at all. World scale only affects VR device tracking and rendering at this point, it has nothing to do with the simulation. It is how you define the relationship between game units and real world units.

Maybe there is some sort of bug, but your use case is precisely what that setting exists for.

I just had the same problem and found out, that it's implemented.

There are VR settings called

FHMDSettings::CameraScale3D

and

FHMDSettings::PositionScale3D

These values are multipliers used by low-level rendering routines of HMD plugins (at least for Rift and Gear VR, these are the ones I checked). HMD head model and positional tracking offsets are multiplied by them.

As of 4.10, they can be changed on runtime only through console commands:

STEREO CS=0.1
STEREO PS=0.1

Calling as above, results in head model ten times smaller.

Console commands can be called through "Execute Console Command" blueprint node.

To see all possible parameters of HMD, look at

FHeadMountedDisplay::Exec()

in HeadMountedDisplayCommon.cpp