Ward, Don't be concerned about shallow water with a long shaft. Check your motor mount to see if you have a couple of notched positions. Also many small motors have a tilt position for shallow water.
As mentioned before, you will be adjusting your rudder as well as the motor when you try for the minimum water that will float your hull.
As mentioned before, you will be adjusting your rudder as well as the motor when you try for the minimum water that will float your hull.