Hello Stefan........................came across this thread from doing research. I have a Seagull Harrier 46, a nightmare of a plane.
CG recommendation is between 140mm-150mm, I'm mid way 145mm. Climbs when throttle is increased, when throttle is reduced it almost hovers if wind is about 20kmh. down elevator is almost constant. I have not checked the wing and stab incidence. This is an ARF. On another thread, someone said that ARFs hardly have their incidence incorrect. But I'm not betting on that.

I was planning to add some downthrust, about 3 degs.. There is probably too much upthrust, if I understand you correctly. Your help is appreciated.

Charles.