Mine was working, or so I thought, by using the steps I had in the original post and without the hidden field. This is an update page. I noticed that the file name being written to the database duplicated the file extension, such as "imagename.jpg.jpg"
So, first I added the hidden form element. I didn't think I needed that as I had bound the default file in the Upload behavior directly to the file column from the recordset. With the hidden form element, I can visualize the process and I know it works. Even though the direct bind to recordset also seemed to work, I still can't visualize the process with that method. So I'm keeping the hidden field.
Still, it didn't solve my duplicate extension problem. Not by itself anyway. Now that I had the hidden field, and the original file name safely bound to a form element, it just made sense to change the update record behavior to the file field, and not the server file name like I had originally.
Works great now! Now I just have to go back to my insert page which also contains and upload and see what crazy things I did on that one.