The manual says to use AN4-12A bolts for all three rudder hinges. As you can tell from the photo they’re a bit too long. I ended up using two AN4-11A’s and one -10A instead. These allow the shank to exit the bracket on the bottom and enough length to get the right amount of threads showing through the nylon nut.

The parts book does not show the felt washers, but they are referenced in the Stinson Service Manual.

Showing the length is too much. Notice the felt washers to keep dust and dirt out of the bearing.

Showing the proper length with just enough of the bolt exiting the bracket.

All tightened with the felt washers installed.