Not sure what you call this modification but I took an acrylic ruler to use as a wing and glued it to the fuselage of my EPP wing to act as a small biplane wing or rearward canard. I had read that someone did this (actually he glued a couple of short stubby wings on the sides of his fuselage in about the same position as mine) several years ago (cannot find the reference article now) and he explained how it kept the airflow attached to the main wing for longer or some such thing. All I can say for sure is that it effectively pushes the CG backward so I can use a heavier battery or motor and that it improves aerobatic performance, gliding and slow fight. Guess it is like flying with flaps on but not as draggy. As one viewer proposes: it gives more lift. I guess it could be a simple as that, more wing area = more lift.
