Custom Property For Remove Duplicates Transform Input Row

Im working through the MS example of "removeDuplicates". I cant seem to figure out how to add custom property for input column.

I added the helper method:
private static void AddIsKeyCustomPropertyToInput(IDTSInput90 input, object value)
{
IDTSCustomProperty90 isKey = input.CustomPropertyCollection.New();
isKey.Name = "IsKey";
isKey.Value = value;
}
I call it from:
public override void ProvideComponentProperties()
{
//...
AddIsKeyCustomPropertyToInput(input, false);
//...
}
public override void ReinitializeMetaData()
{
IDTSInput90 input = ComponentMetaData.InputCollection[0];
if (input.CustomPropertyCollection.Count == 0)
{
AddIsKeyCustomPropertyToInput(input, false);
}
// ...
}

However when I deployed it and added the component to SSIS package - I cant see the Custom Column "IsKey" in the input column properties window.
What am I missing - please help