marc bailey has produced YB spider and a YD bumblee bee and i think TSK has a YB super pastel.
as for the hidden gene. Jared H. told me that some YB sibs kinda look like yellow bellies but they arent. they are something else. and when you breed a YB to one of those "Special" sisb you get a YB superstripe.
but who knows. kinda like trying to identify wat creats a platnum IMO