There's no need for it. Just shorten the view finder. I did it, and it works way, way better. Easily as good as a Z-Finder (and I had one for 3 years).
James Miller, he uses z-finder with the magic arm attached to the handle and some black tape to cover the open areas. But I would go and just shorten the viewfinder.
It's very similar to the Vimeo one. I would not use a magic arm and a Z-Finder. That just adds more stuff to your camera and it takes more time to rotate the viewfinder to your liking. I shoot with the Short viewfinder all the time and I love it. It rotates where you want it and is great for handheld.