I have really enjoyed coming to this tandem forum because of the synergy of the multiple knowledgeable replies, coming from varied backgrounds. Altogether, we really know our stuff, and we don't have too much trouble pointing out the errors of those who do not.
So I like getting more than one answer to any question. Even if they are duplicates, that assures that the answer is correct. Of course, that's not exactly what happens, and there is much to learn from the differences.
One thing I left out is that, pretty much like Mark (but not exactly....), for any given fixed speed I will upshift to stand (usually right before we stand), and downshift to sit (while we are in the process of sitting). Two or three gears with the tight 11-21 cassette that is almost always on the bike (even for Goat Neck last weekend), and less with a wider ratio cassette.