It is impossible to have a hidden pastel or spider gene correct.
Co-dominant will always be visible?
When it comes to Co-doms it is a visual only on the morphs.Now some refer to pastels as being het for the super form.I think its confusing though and i do not use that term.So if someone tries to sell you a snake thats "het" for a co-dom morph tell them nice try and move on.Unless they are refering to the pastel as being het for the super form.