staff-position single multimeasure rest

[David Bobroff]

I want to adjust the staff-position of a single MultiMeasureRest.  That
is, I have an R1 that I want to place hanging from the top staff line
rather than the center line.  This will keep it out of the way of some
cue notes.  I tried:

\once \override Staff.MultimeasureRest #'staff-position = #5

But it does not affect the single "MultiMeasureRest".  How do I do this?

-David