« on: October 20, 2014, 10:27:18 PM »
I just about guarantee it would snap off with a 400f5.6 attached, and that's a "light" lens.
Hooking a 400f5.6 to a E mount camera is much like hooking it up to an EOS M. The camera cannot be used for little more than to stabilize you holding the lens. And if you are hooked to the Lens instead of the Camera the Camera is more that capable of supporting its self.
Ether way unless used as a backup a 400f5.6 is not realty in the use case for a small mirrorless camera. Not to mention that unless it is real stead focusing on that long of a lens with is mirrorless camera is a serious pain. I would stick to using a DSLR for that.
If it is really that much of an issue someone will find the replacement part Number for the mount on a A7s and get an official solid metal mount.