As I wrote before, the mouth on the old jointer plane I got from mia_mcdavid‘s aunt was too large. The method to deal with this is to place a patch in the sole in front of the mouth that extends back far enough to cover the excess that must be blocked. To do this it was necessary to remove a rectangular area in the sole in front of the mouth to bed the patch. I roughed this out with a couple chisels and cleaned it up with my small Stanley 271 router plane:

The 271 is sitting on the sole of the big plane. You can see the patch to the left of the gap cut out for it.

Here is the patch in place:

And glued and clamped down:

A couple notes:

• Doing this to what is technically an antique is a little nerve-wracking, but my charter is to use the big jointer plane. To do this I am entitled to use appropriate methods to maintain the plane.
• I “routed” out an area in front of the sole to bed the patch. I could have done this with an electrical router—It was a lot like cutting out a space for a hinge in a door. However the setup would have been tricky—There is no standard jig. So I think doing it the traditional way was actually faster. Besides, using the little 271 was fun.