Just looked back at that thread which was started by Craig Jez, and if you look at HIS photo, there is no offset at all! Think the main thing is the distance between the piston operating surfaces in the fully closed state should be the same as the original. Even if it is a mm or two different, the hydraulics will automatically compensate without danger arising.
I will be interested to follow this thread as I will need to do similar job next year.
Good luck.
