Hello from the Pacific Northwest,
I found the site while googleing for information on tandem breaks. I bought my first tandem, a 2004 Cannondale RT1000, recently. I've found that coming down hills, the break calipers get so hot that the plastic parts on them melt if I don't stop frequently and put water on them. In particular, a couple of weeks ago I pedalled up Mt Constitution in the San Juan Islands (2,500 feet) with my sister (total load 400 lbs). Coming down, we stopped twice and found the plastic knobs on the calipers soft and sticky until we put water on them to cool them down.
I'd appreciate any advice. I've read http://www.rodcycle.com/articles/brakes.html which says not to use disc breaks on tandems. I chose the RT1000, because my in previous (very limited) experience, I found tandems hard to stop. I like the control and responsiveness of the breaks, but they can't seem to take the heat of more than about a 500 foot descent without overheating.