[MENTION=252763]Flog00[/MENTION] - Go and test ride the Trek T200. Bill McCready (founder of Santana) thinks very highly of the first generation Trek tandems (T50, T100, T200). The share the same frame, and are laterally stiff. The frame is butted Cr-Mo steel, TIG welded. They are not very light, they are stable.

We have a T50. Ibis made a very nice tandem in the late '80s and early '90s - when the come to market, they tend to be expensive.