Measure, how many delta ticks a revolution gives you and adjust the delta to trigger the next station to feel natural when turning the dial. I bent a simple bracket from some scrap sheet metal to hold the mouse in place just above the dial. The black and white threads of the cord wrapped around the dial helps the optical sensor, so try to position the optics above that.
Similar project: https://2dom.github.io/the-radio/ I did not bother to remove parts of the mechanics to make the dial endless, however. Dialling through so many stations that you need that is tedious anyways, so I felt I don't need it.
Oh and by the way, I made the Raspi's filesystem read-only so I could shwitch it of safely with the radio. See i.e. https://hallard.me/raspberry-pi-read-only/