"staves swapped around" are not shown in the NR. So if we can make it
work, the snippet is worth to keep.
I haven't been able to make this work either. Whenever I use negative values as in the original snippet I get programming errors such as "insane spring distance requested, ignoring it". I can put one staff directly on top of the other, but that's as far as it goes.
I can't imagine the use of reversing staves by this method. (After all, you can simply reverse their order in the StaffGroup block.)
-David