can I use a 10 spd shimano front mech with a 9spd triple?

jomoj Posts: 777
edited September 2010 in Workshop
I understand that the cage is narrower on 10 spd front mech but is it significant enough to prevent using them on a 9spd chainset? I need to replace my 9 spd ultegra and would like to do so with the same or a 105 but it seems cheaper to get a new 10spd mech than a new-old-stock 9 spd.
Cheers, Joe