Good points, gang. When this styrofoam glider (at least 4' wing span) is thrown, even slightly nose down into a steady headwind, there must be some bit of assymetry-either a little Dutch Roll or maybe one wing has more scrapes and resulting drag-or both wings are not held at equal angles in the wing slots.
As for uneven forces, even on our older planes we fly, either the turn indicator ball is not installed perfectly in the ADI or a roll spoiler (or two) are bent from too many years of use (maybe a slat?), and we need a little rudder and aileron trim quite often, no matter what the airspeed change. Never mind with intermixed engines "power by the hour".
