Lawrence,
You and John Hunter have much more experience with these crosses than I. Last year on September 20 I saw in John Hunter’s field many nearly ripe seeds on plants of Hillstar x ( Seadream x N. viridiflorus ). This and your outcome let me hope that the compatibility of N. viridiflorus and N. jonquilla is better than my results show till now.
I think N. jonquilla and N. fernandesii are totally compatible.