wrong IPD when targeting HP Reverb headset

Hi everyone,

I'm writing an application that I'm testing with WinMR headsets, specifically Acer and HP Reverb. The app has two modes:
- custom: I have two extra cameras (LeftEyeRT and RightEyeRT) that are rendering into two render textures. I then take those two textures and blit them on the left and right main cameras with the CameraProcessor script (see screenshots below). The extra rendering cameras are placed at -IPD/2 and +IPD/2.
- native: the main cameras (each targeting one eye) placement and rendering is handled by Unity. The extra rendering cameras and CameraProcessor script are disabled.

When testing with the Acer HMD and IPD = 60mm both modes work correctly. When testing with the Reverb HMD and IPD = 60, the native mode works fine, but in the custom mode the stereo images do not fuse at all (if I pick one spot in the image and follow it with a single eye, when looking at it with my left eye that spot moves to the left, while if I look at it with my right eye only, the spot moves to the right, which is incorrect, the movement direction should be flipped). I have to use IPD = 250 to get them to fuse. Any ideas why this is happening and how to fix it? I've attached screenshots of the scene in both modes.

Thanks in advance for your help!

CUSTOM MODE

NATIVE MODE