I believe that on full scale GA aircraft (like a Cessna), the area of the elevators have little to no effect on stability, since they are just floating when the aircraft is trimmed. However on an RC model, the surface is in effect part of the horizontal tail area, since their position is tightly controlled by the servo (assuming enough torque to avoid blowback). So it really is unnecessary to enlarge surface area on scale models.
As a pilot and flight instructor for some forty years, I can tell you that in full scale aircraft the elevator is seldom floating but is usually fixed by the pilots grip on the stick. Of course trim removes the stick force at a particular speed, but any deviation from trim condition results in immediate pressure to counter the deviation. The pilot not only provides a stick fixed condition but contributes positively to stability by resisting deviations from trim before the airplane has time to respond on it's on. Any other technique is simply sloppy flying.
Whether a particular model needs a larger tail is certainly a valid topic for discussion, but from the standpoint of stability, the pilot is a positive contributer and a remote control situation where the feedback is only sight at a distance cannot be as effective as an immediate feedback from the "seat of the pants".