The whole point of set is to have the teeth cut a slot that is wider than the body of the blade. This will minimize rubbing the surface of the cut. And thus lessen heat generated by the friction. Which would melt plastic.
So, I'm at a loss that you are proposing a blade with no set, which will then allow the face of the blade to rub on the plastic. And cause it to melt. From the ensuing friction. And, in addition, provide more surface for the plastic to "grab".
Am I missing something here?