Originally Posted by TandemGeek

I'm 68.5" tall with a 30" inseam and the small size tandems from most of the major builders are an OK fit. My wife is 62" tall with a 28.5" inseam and has also been able to fit on most of these bikes. On the bright side, tandem builders are building their tandems with shorter stoker seat tubes and more steeply sloping top tubes so even someone at 60" in height may be able to straddle the top tube.

Here are some specs from another post to give you an idea of what's out there. Some of these may be a little out of date, but they're pretty close:

Cannondale's dimensions for Med/Small size frame (Captain / Stoker) in inches are:
Seat Tube: 19.0 / 17.0
Top Tubes: 21.5 / 27.1
Standover: 28.3 / 26.6

Santana's aprox. dimensions for Small size frame (Captain / Stoker) in inches are:
Seat Tube: 20.00 / 18.0
Top Tubes: 21.00 / 27.5
Standover: 28.35 / 27.15

Co-Motion's dimensions for Small size frame (Captain / Stoker) in inches are:
Seat Tube: 21.00 / 18.0
Top Tubes: 21.75 / 28.5
Standover: 29.80/ 27.25