OK, the a-mount to e-mount adapter turned up today. Here are three examples from the Tokina on my a7s. The first is in APS-C mode, the others in full-frame. It looks like you can't go below 15mm without some vignetting. EXIF data for the raw images (before shrinking to 33% and 80% quality for upload).
Code:
======== DSC00035.JPG
File Name : DSC00035.JPG
ISO : 100
Focal Length : 11.0 mm
Focal Length In 35mm Format : 16 mm
Aperture : 6.3
Shutter Speed : 1/160
======== DSC00036.JPG
File Name : DSC00036.JPG
ISO : 100
Focal Length : 11.0 mm
Focal Length In 35mm Format : 11 mm
Aperture : 6.3
Shutter Speed : 1/200
======== DSC00037.JPG
File Name : DSC00037.JPG
ISO : 100
Focal Length : 15.0 mm
Focal Length In 35mm Format : 15 mm
Aperture : 6.3
Shutter Speed : 1/200