i have a predisposition to never want any spiders or morphs

[AntTheDestroyer]

Well dominant just means that the homozygous (super) form looks the same as the heterozygous and since here hasn't been a proven super spider that looks like a regular spider and there hasn't been something that has hatched from a spider x spider clutch that isn't a spider or
normal, it is safe to assume that the super spider is a homozygous lethal and therefore a co-dominant trait.

No matter what the allele is, it has to fall under a locus that has two pairs of alleles. So no matter what the mutation is there will always be some sort of homozygous form whether it is a dominant, co-dominante/incomplete dominant or a homozygous lethal.

ALSO: spider does have an allelic combo in the form of black head in that black head x spider can produce an allelic snake that looks almost normal and has no wobble either. It's a weird complex.

This is not entirely correct. First complete dominant is to incomplete dominant as poisonous is to venomous.

Dominance is not only that the heterozygous from looks just like a homozygous form, but more importantly you will have a homozygous which is phenotypicaly identical to a heterozygous that will produce 100 percent heterozygous animals when bred to an animal not carrying that gene. In this case if spider is a dominant morph you should be able to produce an animal that appears to be a spider but will produce no non spider offspring. Following if the homozygous is in fact lethal there is no way to prove Dominance short of finding and preforming genetic testing on a dead homozygous embryo.