Am I missing something, or are we completely overlooking the fact that Spinnerblast x Bumblebee is a Spider x Spider pairing? Besides the offspring viability issues (which should not be overlooked), the OP would only be gaining a Pastel gene from the pairing, which means there is no advantage to this 2-gene female at all.
Since the male already has Pastel in the Spinnerblast (and I won't do Spider x Spider), I'd go with the YB.