I would think the last resort is not to whack it in, but to take some fine sandpaper to the quill to remove a little material. This is often done with modern 22.2 stems to fit them into 22.0 vintage French steerers. Wrap the quill with paper and rotate the stem so you get even abrasion around the diameter of the quill. Again, there may be something else to try, and someone else will chime in before resorting to sanding.