Just to confirm - I’ve just completed installation using the “Content Junction” trick & it does appear to work as far as installation goes. I see HALion 5 is removed, and the installation doesn’t seem to have used any extra space on the system disk at all in the end.
But I can see the problems if the installer won’t crank up if there doesn’t appear to be enough free space.
EDIT: There only appears to be one set of content installed on my machine - none on system disk, one set on D:. (Much of that content is old incidentally - the new vstsound files are just for the new instruments - Eagle, SkyLab, Raven, &c. Though the Eagle vstsound is 7GB!)