LouW,

One of the points of having elevator trim in an GA airplane is not having to hold the stick to hold altitude during cruise. This frees the pilot to do some of the many chores that it takes to manage a flight. Some pilots even steer with slight pressure on the rudder and do very little hands on the stick while in cruise. Very common too are heading hold autopilots that only control the ailerons. None of that covers the original point of the effects of scaling tail surface area in models and why one may not need to increase the surface area.