The galaxies, like the previous models should be installed in a space that gets a lot of school traffic so curiosity can be piqued. Then it is a matter of triangulation to approximate the placement of the 12 galaxies in the exhibition space. Refer to
At this scale it will be necessary to use an area 20 feet across. Use the fishing line to hang the various galaxies and whatever is necessary to attach the fishing line to the ceiling.
Extensions to lesson:
arrange for a deep space viewing with a local astronomical society or observatory
go to a planetarium