Superstripe is a combo of two dominant type morphs. We know that yellow belly is co-dominant but I don't know that anyone has produced a homozygous version of one of the other component (whirlwind or specter). There is some question as to if whirlwind and specter are just two different names for the same morph or if they are two different similar morphs that both make super stripe with yellow belly. Like yellow belly both are subtle morphs but they aren't normal. I don't know Nixer and if this is seriously a proven animal from one of the lines that has produced super stripe but if it is then it's a proven morph although I would argue that "het superstripe" is a bad name.