Barry - dual elevators are good on big planes for sure, allows each half to be carried by one servo. Push rods sometimes are a 'bad option' due to the way the plane was designed. This is relevant to small planes too. Hence with dual elevator servos it is direct for each moving surface area. The saving in weight is negligable if its in something of a 40 sized plane. The extra couple of ounces is hardly anything. I have flown many planes with an elevator pushrod, if its properly done the elevator has hardly any noticeable slop even for 3D.