On our tandem we once pulled a long string of single riders into a 25mph wind. 9.3 mph was it - we were about 60 miles into a century with most of the climbing behind us. The string got long because we kept catching people who didn't look so good. No one went around us and we are not a strong team. When we turned around, we were doing exactly 25 in dead air. People went around us just fine.
I'd rather have the headwind half way than a cross wind all the way on the tandem. With a cross wind, we're both out in it. With a headwind our drag isn't much greater than a single when we're all the way down. There's really no such thing as a cross wind. Your speed will pull it ahead. If it feels like a cross wind, it's a tail wind.