To add just a bit more to what doubledee said, when a full scale plane is trimmed, it is trimmed to aerodynamically fly at that airspeed. If power is added and trim is not changed, the additional power makes the plane fly faster than the trimmed speed causing the plane to climb to return to the trimmed speed. Same for a reduction of power, the plane wants to slow down - thus the nose drops to maintain the trimmed speed.

What ever you do, do not raise the trailing edge with shims. This will change the angle of attach of the wing, and the angle of incidence between the wing and horizontal stab. The end result is a reduced angle of incidence increases the stall speed and also increases the glide speed and landing speed. In some situations it could render the plane very difficult to control ending in a re-kit. [:@]

Like was said before, learn to correct for the climbing tendency with the trim. If you change anything, shim the engine to compensate. When you move to a more aerobatic plane there won't be as drastic of a trim change to deal with, but it will help understand what is happening in all regimens of flight.

Hogflyer