Cross-staff beaming

[Davide Romanini]

Hi,

I have a piano piece that jumps often staff-to-staff. I want that each note has
a beam between the two staffs, not below or above. Generally Lilypond makes
a good work handling them, but for some reason in just a place it places the
beaming below the notes. It's not ugly, and it doesn't change (obviously) 
the music,
but I want anyway the beam between the staffs. I tried to use the properties
height and direction of Voice.Beam, but it doesn't work!

Bye, Romaz