ORIGINAL: adam_one
How much was the wing chord during your wind tunnel tests? and which was the lowest airspeed?
Friction and the Reynolds effect result in an approximately 1⁄2" thick boundary layer toward the rear portion of a 4 to 5 ft. chord wing designed to fly at low speeds e.g. S.T.O.L.
A conventional aileron would thus have about 2 degrees of deflection with very little control effectiveness.
You're assuming that the control surface deflection must be larger than the boundary layer thickness before much force is generated but that is not true. The boundary layer is not some kind of vacuum within which nothing happens. It is AIR, just like the freestream air except slower moving, and is fully capable of transmitting forces.
Allan