HMD view Zooom

I am using a pawn with a camera/hmd attached (from the SteamVR template). I am trying to get the view through the HMD to zoom in and out on demand (binoculars style) on a keypress.

I have tried using a blueprint to change the FOV of the camera both within the pawn BP and the level BP but neither seems to have any effect on the actual HMD view when playing.

In editor mode when I change the FOV settings of the camera it does affect the pawn ‘preview view’ in the little window but the fov resets back to normal when playing the game through the HMD.

I am assuming the HMD is overriding the camera FOV I am setting somewhere but I cannot see where.

Any ideas?