The truck arms extend from the main structure and hold the trucks.  Again I added wire and small bits to simulate piping.  These small pieces are getting rather pixelated due to the resolution limitations of 3D printers.  If you have a resin printer you could get more detail in these pieces.  On the underside I added cable trays which will route the wires from the trucks over to the main structure.  

On top there are attachment points where the LUT sits.  Notice that each corner has a different configuration of hold downs.  The following drawing shows these.  One corner has four, one corner has none and the other two corners have two each that are in different directions.  I have added the other detail NASA drawings for this detail out on the website where I am documenting this build in more detail.  http://www.spacemodels-forum.com