@Phaedrux - Yes, the XY belt layout is to both get around the smooth rods and Z-belt as well as for tensioning - it works great!
The version in the video is using a single Igus 12mm bushing on each smooth rod. An updated version should be ready in the next few days that uses two bushings each.. we'll see if it is necessary or not.
Here are some photos of the z-belt connections. The piece that fits against the teeth is ribbed to properly seat itself into the belt and the holes are over-sized to allow it to properly fit in the front (more on that in a second).
The rear is where the ends of the belt come together. After it is tightened (with the front connection removed), proper belt tension is applied. Then, the XY mechanism (still working on a good name) is leveled. Once leveled, the front connections are tightened onto the belt. The belt is now locked in place and the XY mechanism has no ability to lose alignment.
Yes, the bed itself is adjustable for fine tuning.