jonwvara 

Thanks for the good and thoughtful answers. It does not surprise me to learn that this is not the tandem of anyone's dreams. The frame is no doubt whippy and underbuilt. But the thing is, I wasn't looking for a tandem in the first place. Although I have not yet examined the bike itself, it seems to me that the wheels, crank, brakes and brake levers alone are worth more than the $50 asking price. (Whether or not I actually need those parts, of course, is another question.) And I thought it might be mildly entertaining to jaunt around on the local rail trail a bit just to see what riding a tandem is like. Maybe that's a bad idea--this one is such a bad fit that it will poison my stoker's mind against tandems forever. Sigh.