An overview of Microrax is needed. It took me a while to figure out which parts might fit where. I think that I now know where they go. Dual nut plates in the track, screw through a joining plate, and screw heads are outside. I don’t know if joining plates can be stacked with standard screws or not.
No as you might imagine there is very little spacing between the screw and the extrusion connecting a single plate. The 5mm screws are perfect for a single plate. If you stack plates you will need a longer screw.