Span stem engraver

[Phil Holmes]

I'm updating my Noteworthy->Lilypond converter to take advantage of the 
new-ish span stem engraver.  The simplest way of getting this working is to 
create every pianostaff with the following code:

\new PianoStaff \with { \consists #Span_stem_engraver }

whether there are actually any cross staff stems or not.  Is there any 
reason not to do this?

--
Phil Holmes