Just got our tandem going with Campag 11sp shifters, 11-32 Ultegra Cassette, and Sram Rival WiFli derailleur.
It is basically working and shifting well. The pull ratios however are not quite correct. The derailleur is not moving quite far enough to match the cassette. It is still getting all the gears but only just. I am going to have a go at modifying the derailleur to see if I can improve it.