Wife and I did the Chico Velo "Mildflower" (100K) on our tandem. The one climb, "Honey Run", was certainly tough enough on the tandem. Well-run event, beautiful weather, good scenery (last 20 miles excepted), good food at ride's end. Pulled three singles on the downhill at speeds up to 48 mph, but ran out of gas the last 15 miles or so.