Collision between ottava bracket and stems in cross-staff systems

[Paolo Pr]

Hello,

in cross-staff systems, I see that the ottava bracket can produce an unwanted collision between the "8va" string and the stems. Please, look at:

http://lilybin.com/vf4vaj/1

Is there a way to automatically avoid that, without using the trial-and-error method for adjusting the offset of the object?

Thanks