Upon further research, here are the choices for "fast" tandems that would be fun to ride. These aren't the workhorse, ride across America, but great for a fast century or the STP. Precision Tandems seems to have the best site that pulls it all together along with pricing.
Some options:
"Burley Rivazza Race":http://www.burley.com/products/tandems/default.aspx?p=Rivazza&i=4. This is alumimum, weighs 33.5 pounds. The standard version costs $3,300. You can also get it with Rolf Wheels, Alpha Q Carbon Fork and FSA Carbon Cranks for$3600. The small would fit. It is 56cm for the captain and 79cm standover, so just about the same as my Trek.
"Co-Motion Robusta":http://www.co-motion.com/robst.html. A dream bike but expensive. 29 lbs out of the box. Has a special carbon fiber fork, carbon cranks, Rolf wheels. The 21/18 is 55.25cm top tube with 75cm standover so that is probably about right, although the 22/19 is 57.2cm top tube, so I'm right about in the middle. I've heard that you want it just a little bit shorter on a tandem. This is an all Dura Ace bik with carbon FSA cranks. A breaktaking $7,245 though. "Co-Motion Supremo":http://www.co-motion.com/supr.html. This is a steel bike, but it is just 31.1 pounds and is a slightly less amazing$6,145. Same equipment as the Robusta, but less expensive.
"Santana Team Scandium":http://www.santanatandem.com/newteam.html. They've just launched a new line for 2005. The Team Scandium is a pound lighter than the Team AL from last year. $6,695 for the base model. Not clear what the exact weight is. They use a propritary Dura Ace wheel set with just 16 spokes (wow!). Carbon fork and crankset as well. "DaVinci Joint Venture":http://teamspirit.net/jv.html. This is$4,700 for the base model. Comes in both 26" and 700C wheelsets. Also you can get titanium which saves 2lbs 6oz for an additional $3000. Going to aluminum costs$500 extra. Kind of an amazing component set, they use Campagnolo Chorus, special cranks plus these folks use independent drive trains so that you get a huge range of gearing plus the front person (captain) and the rear person (stoker) don't have to peddle together, so kind of cool technically. Size wise, their medium is 56.6cm front tube and 77.7cm standover. They also have a cool option for kids where called Large/Small Road where the front is 57cm, but the rear is just 44cm instead of 49cm so that really small folks fit well. Not clear the weight.
"DaVinci In-2-ition":http://www.teamspirit.net/i2r.html. The midpriced version of the Venture. Uses Ultegra and lower end shimano mainly. Only comes with 26" wheels. A more reasonable \$3,600. Not clear what the weight is.