Billboard crosshair changing relative size in VR

I have a first person VR project and I needed a reticle for it.
I made it using a Spring Arm I attached to the First Person Camera and a billboard at the end, so it would always project on top of any object I see.
I checked the “Size is in screen space box” to keep the relative size constant.
When I launch it in the viewport/preview window it works as intended.
When I launch it in VR mode, the reticle reduces its relative size as it gets closer to the camera.
Does anybody know how I can fix or work around this?