Originally Posted by
TandemGeek
Look for a used pre-1999 Cannondale RT1000, RT2000 or RT3000 in one of the larger sizes. It should fall into your target budget and will serve you better for your respective and collective sizes vs. the Santana. The reason I say a pre-1999 model is because the stoker compartments were far more generous than they were between 1999 and 2008. They finally came to their senses and went back to longer stoker compartments in 2009.
To know what size (XL/L or L/M) we'd need to know your inseams vs. height as there's a good chance that you both may be able to captain or stoke the same tandem.
Ultimately, the person who feels more comfortable piloting the tandem is the one who should be captain. Technique and team work can go a long way towards nulling out any handling issues that could come from size differences.
I don't think it accurate to call the models you specify "far more generous" in the stoker department. The difference is after all only around 3cm. Sure the extra length is nice but I wouldn't rule out RT's from 99-08 because of it. Most teams don't even use a very short stoker stem to utilize all the length they have.