My husband and I are on our third tandem. We now have a CoMotion Speedster and love it. If you are serious about tandem riding it might be worth traveling to a tandem shop, or writing to CoMotion about sizing.
That being said, tandem riding is a serious commitment. I am the stoker and I cede all control (or at least most of it) to the captain. We are about to do our sixth AIDS Lifecycle (550 miles-- SF to LA) on a tandem and I love that I can ride with my husband all day. if we were on singles I wouldn't see him all day.