Without intending to suggest that running lights are not a good idea, I just wanted to note that they are not required for night sailing on boats of less than 7 meters. The rules state that you must carry "an electric torch or lighted lantern showing a white light which shall be exhibited in sufficient time to prevent collision."

Usually, I'll take a small waterproof light and tape it to my sail, pointing up, near the clew. Makes for a pretty visible boat with the high intensity lights that are available these days.