Upload & Sell: Off
So I got the Mark 4 metabones adapter (ordered directly from MB). A few observations:
1. It now comes with a protective plastic case and two end caps - which should be nice - to prevent dust gathering in the optical path.
2. It's tolerances and quality is pretty much as bad as before, the adapter still moves slightly when mounted on A7R.
3. The inner path does appear larger and it does reflect much less. Putting the two side by side by a light source makes it pretty apparent.
4. So far I tried 24-70mm mk2 on the new adapter, and I have been unable to induce vertical flares (i.e. coming from light just above or below the frame). MB3, with top and bottom unflocked, does exhibit flares from the same spot. I was able to replicate side flares, but they were weaker than a flocked MB3. Haven't tried TS-E 17 yet.
I'm actually thinking of swapping the two mount ends from MB3 to MB4 - but I guess I can contact Metabones first. My MB3 had a perfect lens-mount side tension.