I was under the impression the Startdust/Vivi and Mini Nova all used the same head? Interchangeable with one another?
Is this not the case?
It's not exactly the same head. The Nova heads have a metal cup in the silicone cap, and the stardust heads have a metal nipple. The metal part that the silicon cap goes onto is longer on the stardust head, but the overall dimensions of both heads are very close, so you can use either head in either device.

