Hin Man , Oct 25, 2013; 09:42 p.m.
Malcom, you should look into this adapter as it has 5 steps aperture adjustment that can work with DA type of lens that are without aperture ring. The one you posted only work with lens that have aperture rings. I have the adapter with aperture control for 5 steps. Both Pentax K to NEX adapters are a bit bulky. There is a similar adapter for the M42 lenses and it is even bulkier with a cylinder shape. I don't have the A7 but you can visit my blog page and see how I use Pentax K mount/M42 mount lenses with Sony NEX cameras.
An alternative way to use the Pentax Full Frame capable FA mount lenses with current nex E mount is with Zhongyi Lens Turbo that is a focal reducer that cancels out the 1.5 crop factor on aps-c and the focal reducer adds 1 extra light of stop. The caveats lie in degradation on corner performance. The advantages are FF field of view and gain of 1 stop of light. You can look up Metabones speedbooster and the Chinese knockoff Lens Turbo. The reason that I mention Lens Turbo is that the adapter is almost like half the length of the Pentax K to NEX adapter.
Using the FA 77 and 43 with the lens turbo is great on my nex 5n and so are the inexpensive SuperTakumar 55mm f/1.8, 35mm f/3.5 and 28mm f/3.5. The gain of 1 stop of light work especially well with slower lens as in f/3.5 and f/2.8.