How can I add bass staff to a xylophone staff?

So I have a xylophone staff and I want to add a bass staff for it. Is it possible without adding another xylophone and changing its clef to a bass clef?
(I need to use cross-staff beaming and it doesn't work if it's a different instrument. It recognizes another xylophone as a different instrument and does not let me cross-staff beam the notes I selected.)