There are two aspects to this. Firstly, too much power, like too much airspace below you, is virtually impossible to achieve. As has been said - that's why we have throttles.
Second point is weight. A model which is overweight is bad news - and a much repaired model may well fall into that category. The problem, most aspects of which have already been mentioned - is the wing loading. A typical 40 size trainer with a wing loading of around 16-18 ounces per square foot (provided the basic design and the trim are sound, of course) is a *****cat to fly. A model that size with a loading of, say, 30 ounces per square foot is quite a handful.
The bigger the model is, the higher the wing loading can be and still give comfortable flying characteristics.

Mike