So I learned something interesting reading, with my limited German, the section of the Ju188 manual from which that diagram above was copied. Part of what I love about this hobby is learning about the workings of my subjects and this is a good example. The front spar of the tailplane is linked to a crankshaft (the cylindrical part you see hanging below the spar) that is rotated via a lever connected to a hydraulic actuator. The rotation of this shaft varies the angle of incidence of the tailplane depending on the flight mode. In level flight, the tailplane is level, or at 0 degrees. When full landing flaps are selected, the actuator automatically moves the crank, raising the front of the tailplane up so that a -7 degree angle of incidence is created, which I assume is meant to counteract the nose pitching up when the flaps are fully deployed. The tailplane is hinged to a fixed point on the fuselage at the rear spar, enabling the slight rotation needed.
Cool!
So my scratch-built front spar will get a crankshaft and actuator link as well.