Helper springs

[chris.richard]

Above or below the main springs?

[SUSIT]

Above IMHO & LE

[simon]

Above - then they become part of the sprung mass once they are compressed to sild.
Same theory with a progressive (variable pitch) springs - put the closer wound coils (smaller gaps) to the top (obviously this is not always possible if the end forms are different at each end).
If you put them to the bottom it just adds to the unsprung mass, you might never be able to tell the difference but you might as well do it properly if you can!