When we set our bike up for TTs I found there to be a lot of possible combinations that would difficult to decide on without using a wind tunnel.
Everyone pretty much knows what to do with a single bike and even they say wind tunnel time is well worth while for those that are serious.
A tandem is quite a bit more complex.
For example as the rider increases his drop to the aero bars he normally loses some power but more than compensates by better aero.
But is this the case on a tandem? The wind he may be "cheating" might just get the stoker and the gain might not be there.
Does the captain ride with a forward saddle (triathlon style) to give the stoker more room to tuck their arms and head in?
Does the stoker ride on the bull horns or crunch up a bit and have their hands behind the captain? If they do, do they have their hands close together or maybe a little wider so they are more behind the captains legs?
I certainly don't know the answers, just the questions.