Cross-staff beaming

[Hilary Snaden]

I've just installed 2.13.61 (Windoze binary)

I'm working on a piece with a lot of cross-staff arpeggios, many of 
which need their stem lengths/beam positions tweaked for easier reading. 
The manualBeam function in the manual

manualBeam =
#(define-music-function (parser location beg-end)
  (pair?)
  #{
  \once \override Beam #'positions = #$beg-end
  #})

works perfectly for a few bars, after this the beams and stems of the 
beamed note groups are AFAICT rendered inverted top-to-bottom.

A recent bug-lilypond thread suggested that some work had recently been 
done on the cross-staff beaming code. Is this still on the to-do list, 
or am I missing something? (A workaround?)

--
Hilary Snaden