Hello,
If you render an empty frame from VRay for Maya 2016 the EXR size would be much bigger than if there is something in the frame (5 MB vs 80 kB). I suppose this is related to autocrop, the “exr/dataWindow” metadata is equal to frame size in case of an empty frame.
Is there a workaround with this issue? The first thing which came to my mind is to detect if any geometry exist in frame and create pixel-sise cube cube in the corner if not, but this is quite wired and not easy-to-implement solution.