Moving a hairpin horizontally

[Kim Bastin]

What's the override for moving the ends of a hairpin horizontally? I 
need to start one a little to the right of its default position because 
it collides with a cross-staffed note. But I can only find information 
about moving hairpins vertically. I tried this:

\once \override Hairpin #'X-offset = #1

but this moves the whole hairpin, offsetting the right end too. It's 
such a simple matter there must surely be a simple solution, but I'm 
stumped.