I ended up passing on the used Trek T900. Instead, we went to our LBS and purchased a new Burley Zydeco Mixte-X ( 19 x 15). We tried a Raleigh Companion on for size and it would fit my stoker so long as we replaced her suspension seat post with a non-suspension one and put it all the way down to it's lowest setting.

The Burley on the other hand fit both of us with only minor adjustments to the Stoker handlebar stem height and her seat fore/aft adjustment. There is still plenty of height adjustment left on the stoker seat tube and if she needs the bar closer we can always get one of those telescoping stoker bars.

We took it for a maiden voyage this weekend and both of us absolutely love the initial impressions we got from the ride. The Burley frame in particular is a gem. It felt plenty stiff for climbing and nicely agile for around town. I had the bike shop swap the semi-off road tires that came standard for a set of road slicks and they give a great smooth ride on the bike paths and roads with plenty of grip. Plus, they weigh a bit less and probably offer less rolling resistance for easier spinning.

BTW, I have to agree with the notion that the stoker needs to have adequate stand over clearance. Unbelievably, we needed it the very first time we took took the bike for a cruise. While going around an obsticle on a paved path, I couldn't see that the edge of the path had a ridge hidden by grass that sank into a shallow rut of soft dirt. As I started to rejoin the path, the tires slipped off the edge and suddenly sank enough for both our pedals to strike the paths ridge on the downstroke. This caused me to lose stability for a second. Fortunately, because of the Burleys X frame with tons of clearance for the Stoker, we were both able to quickly get both our feet down which kept us and our new steed from toppling over. I'm not sure I would have been able to do it on my own with a stoker either still seated or leaning on the top tube. As it was, the only damage was to the Captain's ego and some paint scraped off the pedals. Somtimes s*** just happens.