For me the point is that part of the consideration of a disk for is considering if you actually need one. There are many people who do not ride in the mountains and/or the rain and the mountains that can get great tandem stopping power with rim brakes. They are a simple proven technology that saves what would normally be considered a lot of weight over disk brakes.

It is interesting and refreshing to see the subject of weight drop away on this thread. So I with a 36 pound tandem will say I would add disks if I need them but since I feel the rim brakes work fine for us and I will save the weight (and the zing zing) I hear at tandem rallies.