^ There is a reason you don't see Topolino wheels in the Giro or the TDF. They have to be terrible aerodynamically.
Conversely you do see deep dish, low spoke count wheels being used in alpine stages of professional races, precisely because the aerodynamic adavantages still trump the weight penalty even in moutainous terrain.
Another example would be Team High Road using Zipp 404's for the most mountainous stage of the TOur of Califiornia, when they could have gone to Zipp 202's
Another way to think abou this is 1lb off the weight of a tandem is going to be something like .25% to .3% of the total bike/team weight. When you run the numbers through a model that takes into account weight, and aerodynamics that little weight change hardly results in a measurable change in speed.
However, changes in aerodynamic drag do result in measurable changes even at relatively slow climbing speeds.