avoiding collisions between staves

[Bret Whissel]

I'm having a collision problem between staves of a PianoStaff. A
PhrasingSlur in the first voice (stems up) of the lower bass-clef staff
slightly overlaps the eighth-note beams of the upper treble-clef 2nd
voice (stems down).

Is there a way to adjust the staff-staff-spacing of just this one
system? (I don't want to make any vertical spacing changes globally.) Or
can I add more padding to the PhrasingSlur or Beam (or some other
entity) to avoid the collision? (I'm compiling from git sources, so v2.19+.)

I haven't found a related snippet or discovered the correct recipe yet.

Bret