From the many previous posts regarding the inaccuries of this model (Warped wings is an example) I have read that the Engine/wing/tail incidence is not that good.

The first thing I would do to solve the climbing question is to check the tail and engine incidence relative to the wing. All three should be set at 0-0. to start with. If the tail is glued in then prpbably the easiest fix is to shim the wing and/or engine.

There is little point in making other suggestions until the wing warp is corrected and the incidences are correct.

Ed S