yes. Super specter Ivory
Its just like making a super pewter. Which is a Super pastel Super cinnamon. If they both have a super form then it is possible to have double supers in one snake.
Edit: Actually ...do superstripes already act like a super form for the yellow belly and specter?
Edit #2 : I take that back I'm not so sure now. I don't think a super specter/Ivory can happen.