I have aerobars installed all the time on my single bike, partly for aerodynamics and partly for comfort on long rides. I've used them occasionally on the tandem, but we don't tend to do as long rides on the tandem. Plus, the tandem often has a handlebar bag, which prevents me from installing aerobars. For our long tour later this year, I've been trying to think of a way to have both aerobars and bar bag mounted, but haven't come up with a good solution yet.