Disable vsync in VR application

Hi,

I'm going in circles trying to find a way to disable vsync while using an HMD. I understand something has been done to take the ability to disable it from the developers and I'm not here to dabate it. But I do need to be able to overide it so I can control FPS in the application for an experiment that I have to conduct. As is I'm unable to disable that vsync even from the GPU settings (?!) or CLI when an oculus application using bare OpenVR is on.

So my question is this: how to disable vsync with a VR headset? Alternatively: can I change the refresh rate on the HMD itself?