Cool!
Nice system. I like the textures!!
But I don't like the way US2 build rings/dust. The particles are way to colorful and way to big. So I like to manipulate that dust.xml file. I edited your system, take a look. ;-)
Dunno if you know this, but.. ubox files are nothing more than zip files. You can right click it, open with... and chose winzip or winrar. Inside you'll find the xml files of the project. You can edit them, put them back in the zip (ubox) and bam!
Oh a tip: Overtime your big ring will distort. Thats because the turning Z axis of the star are not the same with the ring. So when the star turn on it's own axis will exert different gravity in different parts of the ring. In other words, the plain of the disk is not aligned with the gravity plain of the star.