When a cambered airfoil like on a Cub is flying along at cruise, it often sort of "flattens out" and flies with what looks to us as a bit LE down. Those airfoils don't need much AOA to generate what little lift is needed to carry a Cub's weight. So they don't fly pitched up. They fly almost pitched down. And what does that do to the angle the stab is flying?

The stab winds up (pun intended) being pitched nose down. And it needs to create some down force to stabilize that cambered wing. But not a lot. And it's already seeing a downwashed airflow. So what does the designer have to do to the AOI of the stab to get the needed AOA? He often has to pitch the stab "funny". Sometimes it winds up with a pitched up AOI.

It takes quite a bit of "school house" aerodynamics to figure out AOIs. It's what AE's get the big bucks for. And they then take the answers to a wind tunnel and find out what really works.