My wife and I have been riding our tandem for about a year and enjoy organized rides. While as senior citizens we're not speed demons we'll pass slower rides on the flats. Downhill we can develop some pretty impressive closing speeds. We use "on your left" at slower speeds where passing room is minimal or if we need someone to move over (riding left of center lane for example). In other circumstances I'd prefer to pass with more than adequate room rather than distract the other rider; on real downhills there isn't enough time for the other ride to react. In one situation today I called "on your left" and the rider, who was already 3/4 of the way to the centerline, moved left.

Any thoughts on this approach? This certainly isn't unique to tandems, of course.