Apparently Ikan just announced this:

ikan Intros Elements Stereoscope 3D Camera Support System (http://www.dv.com/article/94012)

Seems like one could easily use one for SI2K rigging for 3D filming. Not cheap at $399 list, but not prohibitively expensive either...

I don't see any form of fine adjustment for pan, dutch, tilt or toe-in. Not that it is not there, just that I cannot see it. This rig will be okay for the experimenters and enthusiasts but it looks a bit too flexible for me. For seriously accurate coincidence of two camera images, I think it may come up short.

My piece of right-angled aluminium extrusion out of the Austal Ships salvage bin with one milled face will do me fine in the meantime.

The SI2K mini heads with all their accurately milled surfaces line up quite nicely with just a straight edge, gaffer tape and rubber bands. That was all that was used on the stereo microscope for the first brief test. Things are a bit better these days. I am unable to post any furthur info as there are some patent and copyright considerations.