Tele conundrum

So my α7r now has its 28-70mm native lens with oss and some degree of weather protection. How nice, given its 1st-generation body has no stabilization within. 

Now I'm covered to 70mm with AF and x.shake..

and then?

A telephoto lens with autofocus, wx seals, and oss by any acronym would be ideal. But where are they? Oh they are out there, but not in my price range..

• The A-mount bodies had IS Inside so didn't need stabilized lenses (in fact Sigma and Tamron removed IS from their lenses in A and PK mounts!), and nearly all were screw-drive AF that would require an ea4 adapter ($200+).
• Sony E-mount native options are few. And recent, so still expensive! The bargains are in the aps-c format (same mount for different sensor size) which isn't quite what I seek.
• Tamron and Sigma have added to the E system.. but w/o stabilization below 400mm. Not ideal, as I'd be happy at 200-250mm but few players sell in that range. Other third-party companies have brought AF primes and a couple of zooms, but no wx or OIS capabilities.
• Oddly enough, the canon EF mount has better and thrifty options for me. $100 adapters are available, and some earlier Tamrons like the SP 70-300 (with oss not vxd) have VC in canon mount. Canon's own 70-300 comes with IS and AF for less, though it zooms in the opposite direction to almost everything else I own. Actually everything I own goes the other direction.. except the Olympus 70-300 monster tele with 43-micro adapter! Coincidence?

First attempts with adapted lenses have been ..instructive. On a 36Mpx sensor, focus is really critical. Images that look all right on a tiny screen look blurry above 1:2 magnification - so AF is more important than IS and wx seals on the α7R mk.1 body. I can manage with the fast Pentax 85/2 and 135/3.5 if I'm careful, but with slower m-focus zooms I revert to focus guessing even when peaking +zoom is enabled.

I test-drove a Metabones EF adapter with the 70-300 Canon IS USD. Many rave about the EF lenses, but apparently this particular lens is older than most and is quite leisurely to AF. And after updating firmwares all over the place it generally misses focus on my test shots. It nearly locks, then shifts one last time toward infinity. Multiple AF presses do not help. That pair is going back.

70-210rs with dumb adapter, 100-300D Apo, 24-105D

So on to plan B: the EA4 adapter for A-mount. That will give me pdAF in the adapter and true aperture control in the body, but better technique will have to sub for the lack of stabilization. The best thing about this option is that I already have the Maxxum trio (photo) so plenty of range is already on hand - plus a Tokina 20-35af. I found an EA4 for less than the usual used price, so that's another plus. And it brings PDaf to the α7R, though at the price of a whiny AF motor drive. Presumably the gains will outpoint the losses on this!

Fingers crossed that this will do the job well enough. 

I'm tired of looking at reviews and specs - especially since I generally miss the one site that says "don't expect this lens and that adapter work right with your current camera body". I've learned that particular lesson more than most.