RE: Should wide,flat trailing edge be included in Chord?
If it's there then it's included. You may not think it's part of the EFFECTIVE wing but it is. It still contributes and enhances the airflow over the forward part of the wing. If you can look down on the model and see the surface area then it counts... all of it.
The efficiency of the airfoil is another whole issue. THIS is where you take all the oddities into consideration, not the area. The odd shape will probably affect the lift coefficient the airfoil is capable of attaining depending on the overall shape. The typical SPAD type flat bottomed shape with flat trailing edge and aileron is much like a reflexed type airfoil. The reflex portion helps you fly the model inverted easier but it will limit the maximum lift you get from the airfoil. But at the same time it helps the model to fly faster. Now if you reversed the trend and glued the lower surface to the upper surface such that the trailing edge and aileron drooped downwards in line with the upper surface then the camber % would be increased, the maximum lift coefficient attainable would rise greatly and you could fly a LOT slower before stalling. However the max flying speed would go down due to the extra drag.
But you would still say you had the same wing area.
That help?