gp staudacher..initial flight....level flight..power...requires some down trim....when power reduced...nose pitches up...needs more down trim.....what's the problem here?

According to this: http://www.nsrca.org/trimA.htm looks like you need some more down thrust.

Actually I'd say you've got too much downthrust. The engine is pulling the nose down and when released by idling it comes up.

But you've also probably got too much decalage as shown by needing down trim to balance the engine's power.

In fact I'd say the best action at this point is to give the whole model a very serious alignment check for all the incidence angles and thrust line angles. It sure sounds like something is out of place. 1/2 degrees count for a lot on models of this type so be very fussy and exact in your measuring methods.

Thanks for help...I agree it's more than a engine thrust proplem since requires nomal moderate down trim on full power..and yet points nose up on idle....does prop have anything to do with this...a dual taper prop 20/6-10........changing incidence on this bird is not easy...since tail and plug in wings are set already. It appears just by looking at motor that there is up thrust....so stilll open for more thoughts