For this post, I will be looking at whether fitting the tough E-mount and reducing the flex at the len-camera mount interface, will translate into better image quality in terms of corner performance (or at least not worsen the performance).
Method: Giottos tripod used in my garden, pointing at the hedge. I used an Arca plate on the camera body to mount to the tripod (to allow for maximum flex of lens-camera interface). Image stabilisation set to off. JPEG out-of-camera used. Centre crop, top left and bottom right of images taken for comparison. I took each shot by pressing the shutter button; one of the things I will do differently in future, would be to use my infrared remote to trigger the camera to rminimise camera shake.
Lenses tested: Sony FE 24-70mm F4 OSS Zeiss lens (at 24mm and 70mm), Sony FE 70-200mm F4 OSS G lens (at 70mm and 200mm) and Sony 85mm F1.4 Planar A-mount lens with Sony LA-EA4.
These are the images from the Sony FE 24-70mm F4 OSS Zeiss lens.
Conclusion: I do not see much difference between the images taken with original mount and tough E-mount. But this lens is not very heavy and hence unlikely to cause much flex at the mount anyway. At least I know that the tough E-mount does not degrade the lens corner performance.