Rostock-compliant bushing carriages, marble joints

I liked the idea published by Etienne Labuschagne in his thing http://www.thingiverse.com/thing:776611
I printed couple of clamps in ABS and played with the joint.
I noticed couple of issues with his clamps design:
1. The joint is quite weak on forces in pull apart direction, though it works well when you push clamps toward to each other;
2. The clamps are too spatial. Being using in my delta machine base it would lose significant amount of build volume in X/Y plane.

So I decide