I use a Ultimate Work stand otherwise known as the Feedback. Very happy with it. Clamp stoker seatpost and place front wheel in a bucket if need to raise the front. I have had a 40 lb tandem suspended only by a seat post clamp but do not usually work with it that way. It is also tall enough to hold the tandem at shoulder height if you like it that high.
http://www.amazon.com/Feedback-Sport.../dp/B0011TKVQW
The picture above does not show the full spread of the legs. They actually spread almost flat making a very wide and stable base. Look at the specs. Other brands with similar design most likely work just as well.
Points to look for. Three wide legs. The wider the base the more stable the stand is. A good clamp that is easy to fasten and release. Do not but a two legged stand for a tandem.
Wayne