Based on the Aux example (credit to JohnB for this which helped me heaps). You need to use the Input iterator code from
viewtopic.php?f=12&t=41964&p=281558&hilit=aux#p242755 to properly get the SuperSource object.
Look for the "if (InputPortType==" line and change to
if (inputPortType == _BMDSwitcherPortType.bmdSwitcherPortTypeSuperSource)
inside that conditional code...
IBMDSwitcherInputSuperSource superSource = (IBMDSwitcherInputSuperSource)input;
//put box iterator here using SwitcherAPIHelper.CreateIterator(superSource,meSSIterator)
I think your create iterator function just needs to use superSource, rather than