If memory serves, a 1/2 wave dipole has minimum gain along the axis of the antenna. Also, the metal structure tends to shield any antenna. So if you mount a 1/2 wave on the wingtip, you'd only be able to recieve from stations off your wingtip.
That's why composite airplanes (made of fiberglass) have their dipoles mounted in the vertical tail, and why metal airplanes have their antennas mounted on the underside (except GPS, which is on top)
In short, that might not be the best place for an antenna.