I actually saw someone who had mounted the Hologon on an A7S but if course there were only two sample photos and they themselves couldn't get to infinity because of a flawed adapter (adapter itself was too thick). If u could get a dumb adapter and prove the Hologon can work with silent shutter mode that definitely clears up some myths! I had the opportunity to use this Lens converted and on an M9 and no doubt the sharpness is there corner to corner.. I recently used one on my G1 too. If only..
About the 90mm, I should be getting mine Monday and will report back.
I keep looking at the 35/2 and 28/2.8 and think I just should get them..
It was a very fast test. Since half the picture was in focus and the rest atrocious, I looked at the adapter and saw that it was mounted nearer on one side than on the other, aka wasn't fitting perfectly, not resting flat on the adapter. I assumed that the problem could rest with the screw activating the focus system on the other lenses, because the 16mm doesn't have a hole for it, so the adapter isn't aligned correctly on the lens mount. A cheap adapter could be modified to take the screw out and then may be (may be) the lens would fit correctly on the mount. From what I've read : the shorter the lens, the more important the mounting precision is.
Concerning the 28mm, may be the A7s would forgiven more than the higher resolution body. But I won't pay much to get it new. The 28mm FE is quite cheap small and one stop faster. It is also very sharp, but exhibit quite a lot of distorsion. Now of course, if you still have a Contax G film body and shoot film too, then the question is different. But the 28mm isn't as good as the 45mm.