I don't use the tripod foot, and I no longer have the A7r. Sent it back. I am, however, working with the Sony A7s. Either way, with these small-body cameras, I tend to put them on rails so that the weight of the larger lenses don't pull at the mounts. Here is a still photo from the A7s, although I bought this camera for video.
Here is a still photo with the Sony A7s and the Zeiss Otus 55mm APO lens. Another photo with the A7s and the Zeiss 135mm APO f/2 lens.
