What Field of View does an Electronic Viewfinder typically have?

I have an old small HDMI display laying around here and I want to use it to create a primitive electronic viewfinder with 3D printed parts for my DSLR.
My design is nearly finished, but I still don’t know what’s the ideal field of view for the user to see the screen.

Does somebody know a typical FOV for a professional EVF in cinema cameras?