Had an email conversation with David Aldrich from D-Focus about this product. Went like this:

Me: Question: Are you guys also designing a rail block to mount to the bottom of the cage? That's the other thing that is wonky with the GH2, getting the lens the correct height off the rails. My concern is that if you're counting on us to use a baseplate from somewhere else, by the time you factor in the height of a baseplate (even one that has height adjustment) and then add in the height of a quick release clamp and quick release plate, and then add the thickness of the cage, there's a good chance your way too high. If you have that problem already addressed, great! I'd love to hear about your solution.

Dave: I do have a rail block planned, but it's pretty tricky with the GH2 as I want there to still be access to the battery door.

In the mean time, the GH2 in the cage, mounted on a JAG35 DSLR baseplate is just slightly higher than the 85mm standard and should work fine in most cases.

Me: Sounds pretty good. How are you mounting the GH2 to the Jag35 baseplate and preventing it from rotating?

Dave: Nothing to prevent it from rotating other than friction at the moment. It works pretty well though. More secure than I would have expected.

When I was test-driving this rig, i used things like this http://jag35.com/products/railblock.html and this http://jag35.com/products/dslrstand.html. That's because that's what was handy, but lots of companies make that kind of thing.

Think I've sussed it. From the same manufacturer - http://jag35.com/new/products/bottom-rods/

I'd be very surprised if they didn't fit their GH2 cage as well

How do rails mount to the cage for a follow focus?

Another video of the same product, just a bit shorter and more casual.