hairpin Y-offset

[address@hidden]

I want to place a hairpin inside the staff.  I have found that I can move 
hairpins vertically with:

\override Hairpin.Y-offset = #'n

...but this will only allow me to move them farther from the staff and will not 
allow them to move into the staff.  I have not managed to find an example of 
this.

Help?

David